Yes, the AA50 sub rules are a bit muddled, but the FAQ helps immensely.
There are no official rules on undoing a mistake, so you’ll have to work that out with your opponent. However, many on-line clubs have procedures for such situations. Maybe one of their members will suggest something here.
By the way, this is the AA42 forum, so questions about AA50 are off-topic here. Please post further AA50 questions in the appropriate forum. Thanks.