EBay Stores
From GarageSaleWiki
You will also need to download the names of the categories you created in your eBay store to select them in GarageSale. Head to the Categories section of the GarageSale Preferences panel and click Update Now in the eBay Stores section. GarageSale will download the store categories for the account that is currently marked as the default account. After this process is completed, GarageSale will tell you how many categories it downloaded from your eBay store.
In the Advanced Auction Options section of the Main Window you can select whether to associate your auction with a category in your eBay store (enable the Use eBay Store checkbox) or upload an item directly to your store (enable the List as a Store item, too) and not in one of the categories offered by eBay.
In the latter case, you will be able to select from a different set of durations defined by eBay for your store items.

