If it genuinely is a ‘slight’ adjustment, then the pragmatic approach would be to do the work and send it as a message attachment… as others have said. You’re a new seller, get that first good review, etc.
However, just be wary that some bad buyers will come back time and time again requesting revisions - often trying to get completely new work completed as a revision, as they know most new sellers are terrified of a bad review or ignorant about their rights on Fiverr.
Hopefully this is a genuine buyer and you’ll be fine. But should they show any sign of trying to exploit you - you have to slam them down straight away and say no.