Thanks for the explanation.
I paid $ for the PS seat actually so no GUC was used for it. I certainly do not want to use a GUC for something I already paid for.
Maybe I should call Delta and ask them to check.
But do they clear in a certain order? Like Delta One has a higher priority to get cleared and if that's not cleared, PS will be the next option?
Ah in that case I would definitely call and ask them to check and remove you from the PS upgrade list. You would hope that the system is smart enough not to charge you a GUC to upgrade to the cabin you already paid for, but ... sometimes the system is not very smart.
If you had booked coach, you have the option to waitlist for both PS and D1, and if one of them opens up before the gate, you get it and the GUC is used -- so if you book coach and waitlist both, you could burn a GUC on upgrading to PS, and would then have to burn a second GUC to upgrade again to D1. So most people choose to only waitlist D1 in advance, and might possibly consider adding a PS waitlist request close to departure if the D1 upgrade doesn't clear. I don't know how it works at the gate if you have both waitlisted, but I would hope that the gate agent would process the D1 gate upgrade list first, and then if anyone was left on the PS upgrade list and hadn't gotten D1 yet, then they could get PS. If I were in that situation I'd definitely be making a point to talk to the gate agent and check though.