Can $250 be $249?

Cathy, I think there has been discussion o this on TPT, and most would disagree with you. Including me. The charity does benefit, in that they don't have to bear the fee. And you apparently agree, because you would deduct it separately.

What makes it separate?

It's an expense related to the donation? I'm far from an expert on this. I deliberately avoid using credit cards for donations.

I think the CC fee is a charitable contribution. I believe it is voluntary. In that case, the donor is, with donative intent, paying an obligation on behalf of the charity. Which leads me to revise my initial answer. The deductible element of the $500.00 is $238.00. Then you are offering the charity funds to pay an expense they incur. So is the full amount of the CC fee, even for the non-deductible element, a donation? I think it is.

Not sure how you were able to itemize with a $256 donation, but that’s neither here nor there, maybe you have other itemized deductions to get you over the limit.

I’m not sure I follow the question entirely, but I would deduct everything paid to the charity, less the amount reported to you as the fair market value of goods or services received in exchange.