The work they do at Macrodata--the "scary numbers"
Any speculation on the work the main characters are doing?
I have a theory on why certain numbers elicit an emotional, often "fear," response from Mark and his co-workers:
It has to do with the chip in their brains and its interaction with code of any kind. The elevator activates the severance chip but also can detect code (letters or numbers or symbols). Since the elevator tech is related to the chip, I think the chip also enables the subject to experience/"detect" code in a different way than a non-chipped person, to the point of seeing certain numbers as "scary."