eBay Always Available setting

On the main eBay configuration page

there is a setting for making an item always available on eBay.



If you select "All items are always available", then UltraCart will set an arbitrary 'available quantity' when listing the item.
You must choose the quantity in the dropdown box that will appear below it (box is visible in image above).

There is a trade-off which you, the listing merchant, must consider.
On one hand, you would like an inventory high enough so that the item is not frequently re-listed. That will help eBay search rankings. Given that, it would seem like 1,000 is a great number.
On the other hand, there are seller limits. If you're new to eBay, the limit could be as low as 100. This limit is determined not just by listings, but by quantity in listings. If your limit is 100 items, then attempting to list a single item with an available quantity of 1,000 will be rejected. Listing an item with an available quantity of 100 will prevent you from additional listings.

So, you must decide what the right available quantity is.
A good formula would be (selling limit) / (number of items to list) = available quantity.
You must also consider the popularity of one item. If one out of ten items is very popular, then set the eBay inventory quantity for that item (Item Management

[Select Item]

click eBay tab at top of page) at a high level and make the default for all other items low.

To find out your limit, visit http://pages.ebay.com/help/sell/sellinglimits.html and scroll down to the section titled "How to find your limits".
UltraCart cannot access this information, so it cannot automatically calculate a good number for you. You must determine this yourself.

As your eBay success increases, so will your selling limits. When they do, you may wish to revisit this setting and increase it.