I think this would be a situation for the ward finance clerk to fix. As long as someone can verify that it got into the hand of a member of the bishopric in 2020, it can be counted as 2020, even if deposited in 2021.
The clerk will likely have to contact support. I'm not sure as GSD is going to help without some local confirmation about the date the donation made it into the hands of the bishop. GSD would have no way of knowing that. All they would know is the date the donation was processed.
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