for values of
A common rhetorical maneuver at MIT is to use any of the canonical random numbers as placeholders for variables. "The max function takes 42 arguments, for arbitrary values of 42". "There are 69 ways to leave your lover, for 69 = 50". This is especially likely when the speaker has uttered a random number and realises that it was not recognised as such, but even "non-random" numbers are occasionally used in this fashion. A related joke is that pi equals 3 - for small values of pi and large values of 3.
This usage probably derives from the programming language MAD (Michigan Algorithm Decoder), an ALGOL-like language that was the most common choice among mainstream (non-hacker) users at MIT in the mid-1960s. It had a control structure FOR VALUES OF X = 3, 7, 99 DO ... that would repeat the indicated instructions for each value in the list (unlike the usual FOR that generates an arithmetic sequence of values). MAD is long extinct, but similar for-constructs still flourish (e.g. in Unix's shell languages).