What to charge Cleaning up audio for a video already done

[Z car guy]

Hey guys ! I'm still learning things about DP here . I just got a small gig cleaning up audio levels and EQ for a video from one of my customers that I do High end Home AV stuff for . They sent me a Video they already had the audio track and it was all over the place in levels and EQ . I fixed a lot of it with automation . I am waiting to see if they can send me the tracks separately too for next video . This is all done remotely on their end . The main question here is what is a fair price to charge for this stuff as I have put 4 hours in on a few versions of edits ? I would fix and they would then ask for more changes so it kept goin back and forth which everyone was fine with that . I just want to be fair on my time and keep it worth my time . Thanks