I took a look at the bill & it appears that he has deducted $800 from the bill. It was $850 for the sand blasting,$850 for the bead & $500 for priming. It also states what was to be bead & sand blasted.
Keep detailed records of ANY expenses related to correcting his mistake(s). Although he may have deducted $800.00 from the bill, that may only be a fraction of what it might ultimately cost you to remedy the situation.
