I have limited membership and have 206 free swaps.  I assumed the system automatically used my free swaps, but the number just goes up, not down, of free swaps I get.  I'm just not sure how this works or where I can look to see how they are being used...if at all.

Maybe this will help -

https://www.paperbackswap.com/help/search.php?terms=free+swaps

I would think that they are being used if you are not required to pay the .49 fee in addition to a credit when you order a book.

It looks like you use Printable Postage so you earn a free swap each time you use that to ship a book.

At the top of the page near the center it says credits then one over says free swaps. If you click on swaps you should see how they are being used. Although it only shows 6 months worth on transactions on mine.

Here is an example of what my page says:

Action: Free Swap for Printable Postage

Hope that helps.

To clarify, free swaps are earned for every book you mail with printed postage (you also get the automatic credit on each book when marked mailed) & standard members will actually never spend free swaps; limited members use them only after 30 swaps annually. Extras not used will roll over annually. For example, I have always been a standard member and have earned 20 this year for a total of 90 free swaps for sending books with postage & have never spent any. Since the free swaps accumulate on your account, if you ever change account type they could be used instead of paying the swap fee. As a limited member they would be used if you were to order over 30 books in a year & al a carte members use a swap every time they order a book.