u/zufallsgeneriert

I bought this wheelset used today and found this weird streak on it. The surface is as flat as the rest of the wheel and there is no difference in knocking sound. So I'm confused if it is resin, bc it doesnt seem to be a crack. I checked the inside of the wheel and there is no sign of damage at all

Seller seemed trustworthy and said he checked for cracks, the packaging from the shipping was really secure.

Is it cosmetic and safe to ride or should i contact the seller for a refund?

Appreciate the help