Avis looking to overcharge

I rented a vehicle. The vehicle has scratches on the wheel caps, and was not completely taken care of and has some chips on the windscreens. After 2 days of returning the vehicle i get an invoice for an admin fee for repairs to the vehicle windscreen for chips. The cost of the repair is R360, and the fee is R415.

Here's my issue: surely the previous person responsible for the damages would have had to pay fees to repair these, why were they not done? Secondly, upon return there were no issues, where do the chips come from all of a sudden. PG Glass charges R250 per repair incl vat, how did you get to R360?

If there were damages pointed out during the return, I would agree but I cant guarantee that a stone was not picked up by a passing vehicle on this one while in your possession.