There is no way to tell because individual fish are so variable in amounts of pee
But the 5ppm is designed for probably an overstocking that you would not do. BUT, its designed that way for a different reason, the reason being that it can be a bit of a fragile period right when you switch over from using pure ammonia to using fish. The pattern and probably "quality" per se of the ammonia flowing to the bacteria changes at that point from the "pulsed 5ppm pure ammonia" over to the "small continuous" pattern and the bacteria are living things just like fish, so any time you make changes you have the possibility, hopefully remote, that it will affect them.
RDD discussed this quite a bit back when he was designing our Fishless Cycing article. He had to choose a single point along a sliding scale of possibilities. Personally, I think his choices have turned out really well, judging from the successes of so many beginners here over time. His method has you switching over to fish at a point when the colonies are really robust and can handle it, even though they will indeed get significantly more robust over the following six months or even a year.
Personally I don't really think its a great idea to max out the stocking right at first, even though its designed to handle that. My own feeling is that usually there is a sub-population of the chosen community of fish that are thought to be more hardy and by starting with only those, you allow the "big 5ppm" bacterial colonies to only be forced to handle, say, 3ppm and thus the drop back and are even more "robust" for the 3ppm load. (does that make sense I hope?)
~~waterdrop~~