Posted By:
fkwIt might be that the cards were numbered right to left. I have never seen a complete strip of the W9316 cards, but have owned at least one of each of the 10 cards at one time or another. It might be that the other 20 cards are nonbaseball cards which is very common with the 1920 W issues.
Here is a W521 card with the "20 to a Set" on the right side (card #20)

BTW is anyone who edits the Standard Catalog is looking, I believe the card listed as "W519-2-2 #20b Schange" doesnt exist (it is the W521 above, or a W519-2-1).