Farming rewards are calculated by the network to balance supply with demand.
Other kinds of reward have been discussed, and when quantifying them they have been related to farming rewards - this I imagine is because they need to vary in a sensible way rather than be fixed in Safecoin, because the value of Safecoin will no doubt fluctuate. So the obvious thing is to relate them to farming rewards.
So if X is the farming reward, what do we thing should go to App Devs, or content publishers, or any group we decide should be rewarded? Well, the sensible way is to apportion it relative the the farming reward: so 10% of the farming reward means “0.1 times X” etc.
I think that sums it up. It becomes confusing when people talk about percentages of the farming reward because firstly there’s a tendency to treat the farming reward as a fixed amount, which is now being split up amongst other parties - but it isn’t because the farming reward is determined independently according to supply and demand.