I've been trying to repair my file for hours, trying to add 10,70km for my totals.fit file. Nothing seems to be working, I'm getting error:
I've been trying to repair my file for hours, trying to add 10,70km for my totals.fit file. Nothing seems to be working, I'm getting error:
Unfortunately, if this was a recorded activity, there's almost zero data in it.

Probably my fault, as I don't understand what you're trying to do. Maybe someone else can have a look.
I see. Maybe this thread should be moved to the Edge forum?
Are you moving from one Garmin Edge to another, If you still have your old Garmin, you should try doing the profile backup as described by aweatherall here - Profile backup when exchanging unit ?
So how many miles do you want it to have?