When using ServerRewards as the currency for Kits players are allowed to redeem kits without having the correct amount of ServerReward points. thus giving them a negative RP balance which they can keep doing . Is this intentional? 

This thread might contain a solution for your problem
https://umod.org/community/rust-kits/33066-kits-with-server-rewards-is-allowing-players-to-go-negative-rp

Thanks