Joshua, it will likely be declined as you would only be able to order a 10rd magazine model which is not in stock and not the 13rd model.

Unless you're law enforcement, your FFL cannot transfer the pistol to you... with the magazine. You might be able to get him to transfer the pistol to you w/o the mag, and that will be fine, but that's between you and him whether you want to do that. I'm kind of surprised that an online retailer would have sold you the pistol in the first place, with a CA shipping address. Chances are they'll catch the mistake before they ship it and deny your purchase, or maybe, just maybe, substitute a 10rd magazine, but that's unlikely. Whatever happens, one thing is certain: You ain't getting a 13rd magazine! Sorry to be the bearer of bad news... but FWIW, I share your pain.

10 rounds
The stay in the ruling means California gun owners cannot buy magazines that hold more than 10 rounds of ammunition. They can keep large-capacity magazines they own.

Unless you’re a law enforcement officer, you can’t have it. It was my pleasure to assist you.