In this system, rewards rate is based on player permission, you can set different reward rate for VIP players or MVP players.
This also can be a check, if players already have VIP rank, they won't be able to get VIP rank reward because you set this rewards rate to 0 for players who already have VIP permission.
Enjoy this update, more features will be added soon as we recode prices and rewards system in past 2.0.0 update.