Heavy handed editing? Not like Pynchon to explicitly define jargon (hash total and Luhn checks slip past without comment on the very next page).
Consecutive invoice numbers. Hash totals that don't add up. Credit-card numbers failing their Luhn checks.
If you were looking over invoice numbers, they'd be more random, not numbered consecutively. Consecutive invoice numbers imply someone was just making them up in order, as the probability is they wouldn't be in consecutive order.
A "hash total" is just a batch total done on one or more numeric fields which appears in every record. This is a meaningless total, e.g., add the Telephone Numbers together for a number of Customers. It is used as a verification device for documents or records. For example, the dates of letters in a file may be added and separately noted as hash total. Thereafter, to ensure that no letter has been misfiled or substituted, the dates are re-added and the new total is compared with the hash total. Wikipedia
The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in US and Canadian Social Insurance Numbers. It was created by IBM scientist Hans Peter Luhn and described in U.S. Patent No. 2,950,048, filed on January 6, 1954, and granted on August 23, 1960. Wikipedia
aka phony baloney
Traditional Russian song used as a musical track on Tetris. Pynchon also referenced Tetris in Against the Day  Hear it.
the plaintive folk tune
Referring to the song above. Any connection to the passage from page 1 of The Crying of Lot 49 that mentions "a dry, disconsolate tune from the fourth movement of the Bartok Concerto for Orchestra"?
- I doubt it. Pynchon is pretty well-versed in classical music, and "plaintive folk tune" clearly refers, as noted, to the Korobushka.
I see a slight connection, maybe not even intended by Pynchon, but one that can still be made. With Korobushka, Tetris and the "plaintive folk tune," you have the linking of something garish, a video game theme song, "the anthem of nineties workplace fecklessness" with something more soulful. The fourth movement of the Bartok Concerto enacts something like this. From an online program guide to the Concerto: The fourth movement ("Interrupted Intermezzo") plays with clichés of "innocent" folk music, while the rude "interruption" is often claimed to represent Shostakovich, whose Seventh Symphony (the "Leningrad") had recently become a popular rallying cry of resistance to the invading Germans. (The music that is allegedly being parodied was itself intended by Shostakovich as a savage parody of the forces of totalitarianism). Other interpretations, however, have challenged that longstanding view of Bartók's intent.
just downloading some shit, 56K's a awesome speed
In reference to 56Kbit/s, a moderate speed at the time for downloading from a file sharing website like, say, the immensely popular Napster.
the li'l goombas of Web design
a reference to Super Mario Bros.
Zima's the bitch drink of the nineties
This lemon-lime malt beverage was immensely popular in the years following its 1993 debut by Coors. It eventually gained a reputation as a girl's drink and was discontinued in 2008. Wikipedia entry
Fabian's Bit Bucket
In computing, the bit bucket is jargon for where lost computerized data has gone, by any means; any data which does not end up where it is supposed to, being lost in transmission, a computer crash, or the like, is said to have gone to the bit bucket — that mysterious place on a computer where lost documents go, as in: "What happened to that important spreadsheet that I was just editing?" OR "Oh, it went into the bit bucket." Wikipedia entry
A physician whose subway ads were all over the NYC subway for 30 years.
File:800px-Dr Zizmor Subway Ad.jpeg
a single over on Rikers
a year in prison
Time is what the Stones call on their side, yes it is.
"Time Is on My Side" is a song written by Jerry Ragovoy (under the pseudonym of Norman Meade)and made famous by the Rolling Stones in 1964. The chorus: "Time is on my side, yes it is."
Trichology is the branch of dermatology that deals with the scientific study of the health of hair and scalp. Trichologists themselves are not normally licensed healthcare workers, although members of the medical profession can undertake courses and/or careers within trichology. Trichology can be used in forensic studies of hairs to find suspects. Forensic trichology can determine the approximate age, body mass, race, and other important traits of the hair's owner. Trichologists are loyal to the academic study of hair loss science. http://en.wikipedia.org/wiki/Trichology
a lemon-lime alcopop haze
The reference is to the Zima drink, of a class of what is called “alcopop," very sweet alcohol drinks which are popular with young people. Zima has a lemon-lime flavor. Wikipedia