Hello NewKal, well there are plenty of tutorials explaining this.
Here some basics
In this case the numbers: 62, 59, 95, 1409 and 7205 are weapon indexes
A group has a group index: 2 and every items has his droprate which is 300/10 = 30% for index 62
;G21 Weapons
(Group (index 1) (Item (300 62...