AoB is set up to help you accurately list your items to eBay, using Item Specifics information for items that are not in eBay's catalog.
The following paragraph or two relates only to new listings that are created directly on the AoB Single LIst Page. Each of eBay's categories have their own set of Item Specific fields and you can populate each category's fields to display on your listing page by entering the Primary Category ID number to that labeled field located in the eBay Attributes section of your listing page and then clicking the Populate Product ID button at the top of your listing page for the population of these fields to take place. You can do this at the same time that you're entering your item's ISBN/UPC/ASIN and populating all of the listing data that is supplied via Amazon's MWS when creating your listing or after creating the listing at any time.
If your item is in one of the Book/DVD/CD categories, the more commonly used fields in that set of Item Specifics will mirror some of the content of the product data column of your listing page. Meaning, for example, that if you entered '261186' for eBay's book category to the Primiary Category ID field, when you clicked the Populate Product ID button the title, author, publisher, media and language fields will share their values to the corresponding fields in the Item Specific section of the eBay Attributes displayed on your AoB listing page. That information would then be sent to eBay in your upload to list the item, or to update an item already listed.
For existing active eBay listings all that you must do to update existing listings to eBay is to send a Refresh to eBay from the Tools page for items already on eBay. As long as the Category ID is correct the updates will send the Item Specific information to the Venue and your items will update correctly.
As an aside, AoB just recently added a new field for Language to the Product Data column of your listing page. You can populate the product data from Amazon for the Language to fill in here and in the eBay Attributes > Item Specific fields. To pull in this important value as it's required for some eBay product types, the easiest and quickest way to populate this information for your full inventory is to request an Inventory Download from your AoB account. Open this file in your spreadsheet and then cull down the columns so that only sku and isbn remain of the file. Save this file and upload it to your AoB and we'll ping Amazon for the product data you need, including the Language if that data is present in Amazon's catalog. When your file is done processing it'll queue uploads to the venue so you would not need to do a refresh.
Writing it all out just now seems like it's a little thing though we're sure it'll feel much larger. As always my advice is the same... one step and then the next to get where you're going. Ask all the questions you need, either on this post once you've signed in with your AoB login, or by coming to Live Chat, or create a Support Ticket by clicking the link on any AoB page.