Prioritizing your work. What you are doing, why you are doing it, what’s going to be the best return on your time, what is your capacity to actually accomplish things and are you overloading yourself so that you have to rush everything constantly.
input = available expendable resources?
output = created resources?
Naturally, the output is constrained by the available input. If a KR doesn't take into account the available input, then it is prone to be unrealistic.
Not the OP, but to me inputs would either be leading indicators or something like “shoot 1000 3-pointer/ every day” and not “get an NBA championship ring”.