It’s best to always enter the amount of weight you moved in an exercise in order to get the best value out of the statistics. For body weight exercises, just enter your current weight. This works perfectly for exercises like pull ups.
For assisted exercises, log your body weight minus the assisting weight. For example, you weigh in at 120lbs and do a bunch of assisted pullups with 40lbs of plates on it, you would log 120lbs-40lbs=80lbs.
For other exercises like push ups, what I did is put my hands on a scale while doing pushups. Turned out there was around 60% of my body weight resting on my arms. So that’s what I enter for push ups.