The short interest data is collected on the 10th of the month, so, this month, it reflected trades made through November 5, when AMD was about 17. The short interest is probably down 13.2M shares mostly because a lot of convertible debt was replaced by shares, and many of the holders of the CV debt probably had shorted the stock to lock in a fixed return on their investment. So most of the stock received would have immediately been delivered against the short position.
But I haven't checked how much new stock was delivered by November 10.
Petz