This class is used to simulate an array that increments in a predetermined fashion as you go deeper into it. When creating a virtual table you may specify 10 levels at which the increment value changes, and ten corresponding increment values, as well as a base value to start with. The  operator will return the value that would be at that position in the 'array' based on the increment settings.
This is meant for use in place of arrays such as the stat_app tables in ROM, which I've seen a few MUDs extend as far as a max stat of 255. You should only use this for particularly large stat tables (keep in mind, each instance of the VTABLE class has two arrays with 10 positions each), and should always run some kind of test to preview a stat table in its entirety before putting it into actual use, but by using this you'll save yourself some time and/or effort.