Poe.trade currency in stock??

Does anyone know how to display an amount in stock??

I go to the site, Manage Shop, and put up currency rates that I'm offering. And they show up in the list. But I have no option to modify stock count, while I see most other sellers have theirs displayed.

If you use a premium tab to sell currency I think it displays the amount in stock, since it is actually looking at your tab.