The percentage covnersion has already an open ticket:
As for the time, since is per session is not something you can edit on that page. You have to go to the specific session itself.
My suspicion is that being able to update the total time on the Edit page is incompatible with how the current data is stored and also because it would break the graphs.
This graph would for example be impossible to generate if I just went ahead and edited the total time
