Hello CMS,
Thanks for contributing to our forum. It sounds like rather than selecting the radio button for "Lots" you should just choose the radio button for "Individual Items" then set your quantity at 20, or for however many of your item you are selling. Since you are selling multiples of the same item, you can just indicate a quantity available and your buyers will be able to select how many from this quantity they would like to purchase.
You would want to use the "Lots" feature if you had say 6 total items but were selling them in groups of twos. In that regard you would choose the radio button for "Lots" and then configure the "Number of Lots" as 3 and the "Number of items per lot" as 2.
I hope this helps! If you run into any further difficulties, please contact our Customer Support team by mousing over the “Help” tab in your Auctiva account and selecting the “File Support Case” option and we will be happy to assist you.
~Michael