There isn’t a set or average amount of time. It depends on how similar the photos are, what issues each has, etc.

Charge them by the hour. Make sure they provide detailed criteria for which ones they want.

Sometimes things get labelled incorrectly.

You’ve just been using the one card?

Yeah, don’t do that.

Everything breaks eventually. Things you use thousands of times a week break sooner.

You didn’t focus on what you wanted to focus on, which is very easy to do with that camera and that lens since there isn’t a focus screen and you were doing it manually.

Entirely depends on the type of photography you’re doing.

I can shoot the outside of a building or tabletop product photos with a 50% keep rate.

Pinup photos with a first time model? I tell them that 1% awesomeness is success.

If you can’t remember your intent when it’s time to edit, write it down. That will help you be more intentional when you shoot. It was what photography students had to do pre-digital.

Also, start analyzing what went wrong with the 99% you don’t use so you can stop doing those things.