The first bug i found is that sometimes, you can't actually but the item even if you have it. (I think it has something to do with nbt values, but they're invisible). I can buy the to xp bottles above for glowstone but not with the large. Same with the other xp bottles for, gp, blazepowder and ghast tears. 
Then when the item is out of stock it turns it into like another quantity. Maybe it's not even when the stock ran out because the one that's 10 small xp bottles was 64 but then turned into 10 for some reason even when it had stock.
Then when the item is out of stock it turns it into like another quantity. Maybe it's not even when the stock ran out because the one that's 10 small xp bottles was 64 but then turned into 10 for some reason even when it had stock.
