Let me shed some light on this.
I won the GS 13 and the DS 11. When I tried to pay, ebay wouldn't let me, saying I would have to lose one of the purchases. It still didn't work. Dave called ebay the next day but no go. Ebay couldn't fix it.
Dave told me he set it up as a BIN with my final hammer price. I tried but it didn't work. I go to the boards and find a link to the auctions on this thread. I put in 2 bids.
When I go back to my emails, it tells me I've won the auctions.
I have no explanation for this and since I got what I wanted, I didn't query Dave any more.
Throughout Dave was courteous, patient and friendly. I hope he posts more of his magnificent books.
The DS was an upgrade, while I have been on the hunt for a GS 13 ever since I foolishly sold my original low grade copy that I bought for $5.00, a long time ago.