http://wiki.project1999.org/index.ph...bat_and_Damage
specifically says the formula you quoted is for "other emulated servers and may have been changed on P99". not having looked at this in a while I suspect that means, as with ZEMs or other details, the devs have not released the actual formula used on p99 and so someone would need to do lots of parsing and figure it out. if so, feel free to update the wiki with your findings!
all the references under that wiki section are linked - it is just a synthesis of that information