18.12.2015, 13:59
Yep, thats an uncommon way, it would be the easiest (and normal) way to use an quadratic funtion. The numbers obviously are based on one (similar to lolumads result, though an aproximated curve wont ever be 100% exact for the reasons given above), probably even with simple coefficients, but I guess single ranks got slightly adjusted manually for better balancing. This especially makes sense, as the "power" of rank rewards differ a lot, and so some ranks should require more or less time than they normally would. E.g. Rank 4 just unlocks a flashlight, while other ranks unlock a whole arsenal of new weapons.