I am so confused by this mod...

I don't have all the stock levels entered yet and on some items if you try to order it, it tells you it's out of stock, on other's it doesn't say anything.

example 1
small= 1
large=2

so someone tries to order a medium (which isn't entered in yet), and sometimes the cart will let them checkout, other times it will say it's out of stock.

Doesn't make sense to me that it isn't doing the same thing everytime for every item.