it doesnt say he has 20 it says "The opposite side reads "20"" unless your reffering to the "Individual Chips: 20"
The auction Skip won the seller says the bottom in the Question & Answer section that he had 2

heres the link to Skips..
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130156233444#description

"Q: I just placed a bid on this chip, do you have any more of these or other denominations available? Caribeislands Sep-22-07
A: No, I only have one other and it is identical. I will most likely only sell this particular chip. Thanks for the bid.
Q: Hello, Do you have more of these chips? I definitely want it in all colors. Rich Sep-22-07
A: Hi Rich. Unfortunately I don't have it in any other colors. This is the only one I have to sell. Thanks.
Q: Hi, how did you get this chip? Any other denominations from the same series available? Regards Sep-22-07
A: Hello. I purchased this from an antique show. Unfortunately I do not have any other denominations from this series. I only have one other from Camaguey and it is of the same denomination."