Allow negative amount in inventory NOT selected, but I still got a backordered sale

‘Allow negative amount in inventory’ is NOT selected in my admin settings.

track inventory is, and for the most part the inventory tracking seems to be work well.

However, today I recieved an order that came into the system as backordered, and a notice that the inventory level for the item sold is now -1

How can this be if I have the system set to NOT allow negative stock values???

Am I missing something here or is there a glitch in how the system is tracking inventory, maybe related to held cart items or something??

Not sure what version you are on but on I get same on old 2.07