A few people have asked about this, and I don't think it's correct, so here's my understanding of what happens if you paid in full and decide to cancel:
The parks were closed from 03/16/2020 through 07/11/2020. That's 117 days.
Disney looked at the date your AP was set to expire, and added 117 days to it. Think of that as
the extended expiration date.
If you decide not to cancel, Disney will add another 30 days. I guess we could think of that as
the extra extended expiration date.
If you cancel, you will get a refund "for the remaining access days of your annual pass from July 11, 2020 through your pass expiration date (as extended, if applicable)."
So if OP's pass was originally supposed to expire on 10/15/2020, the extended expiration date would be that date plus 117 days, which takes it to 02/09/2021.
OP should get a refund for 07/11/2020 to 02/09/2021.
My guess is that if OP had a pass with block out dates, the number of block out dates would be subtracted when calculating the refund. I think that's what "access days" means.
However, even if OP called today to cancel, Disney is not processing the cancellation as effective today. "Your pass will remain valid through August 11, 2020 and will be cancelled effective August 12, 2020." That is what is confusing. It seems to mean that OP could use their AP tomorrow or any other days through 08/11/2020 and still get the refund as spelled out above. It also would explain why people's APs are still showing in
MDE even after they called to cancel. In fact, MDE might show their APs as having the extra extended expiration date. So if OP looks in MDE, OP might see their AP with the extra extended expiration date of 03/11/2021. If I'm correct, OP's AP will disappear from MDE on 08/12/2020.
The language I put in quotatino marks is from the confirmation email you get after you cancel.
If people think I'm wrong, I'm sure they will chime in.