There is no way to edit the quantity at auction for inventory items in SMME, the Sales Manager Edition you are using.
What I would do is just add the quantity of 6 that you removed from the store to your quantity available. The eBay item will not sell more than the 4 that are in the auction.
I don't think the Quantity at Auction updates while the item is live, that is, it does not look for and will not reflect the kind of change you made while the item is live.
When the items ends, you might want to double check that the shift of any unsold Quantity from "At Auction" to "Available" reflects the Original Quantity at Auction. (there is a slight possiblility that as the item closes at eBay, Vendio will *then* recognize the change you made earlir and adjust your quantities. If this happened, the adjustment will have happened twice and your Qty in Stock will be larger than it should be)
Basically, manually edit to your Quanity Available to reflect what you did, but babysit it a little at the end to make sure your numbers are accurate after the item closes. (This is a pretty rare case, so I cant be completely positive how it will behave)
Best,
Abe
