Right, here's what I just found out...
If you follow the instructions for an unmodded car, it will treat 6 tanks using 50ml, for a modded car use 100ml, and if you're doing a track day, just put the whole bottle in, it's like a vindaloo for the car
The RON increase is 6RON, so if you're using Ultimate or Optimax, it should give you 104RON....