I guess the algorithm for specificity in all modern browsers involves a base-256 number. Why? I believe there are 4 slots for specificity - class, id, !important, and styles defined in the tag. 256^4 = 2^32, the size of an integer. Unfortunately we get this is as a side effect.
According to the CSS 2.1 spec, “Concatenating the four numbers a-b-c-d (in a number system with a large base) gives the specificity.” Base-256 is the obvious way to encode each digit efficiently, and I suppose all browsers that do this are still in compliance with the spec.