This ends up being amortized in per-minute increments, so that for every 15 minutes you’re driving a passenger, you make $4.
Now, this doesn’t mean that if demand is low in an area or its 2am and no one is searching for a car that drivers still get paid for time they drive around without working. There have been legislation attempts to do that, but they’ve failed (notably in California and other places).
You aren’t paid by any of these services for the time you spend seeking out a passenger — which is the same way taxi cabs work. Work time begins and ends with the ride itself.
That’s actually one of the criticisms made against these types of requirements, because there is an argument to be made that if fares rise too much, that will suppress demand (and especially suppress demand in lower-income areas), leading to drivers spending more time driving in circles trying to catch rides, so that their net income is less than it was before. The related part of that argument is that it will lower driver availability in areas that are hard to get to, leading riders in those areas with fewer options, regardless of how much they are willing to spend, because drivers are choosing to stick to heavily trafficked areas.
So a driver can still use both services, but they can’t double-dip, because it isn’t possible to drive two passengers at once (I mean, I guess it is, but that activity would get a driver banned from both services).