inventory incorrect - error with sold items

[misscherylb]

Hi, could someone explain please when exactly VM logs a sold item as sold in the inventory? Is it when the status is set to "confirmed" or "shipped" for example?
Our inventory figures do not match the figures from the order... trying to figure out why some items sold and reflecting in "orders" are not counted as "sold"?
But then all orders have in fact gone through the process of being set to "confirmed" and then to "shipped"...

Also, some items that were sold once or twice don't say sales 1 or 2, but instead have this error figure in there: 4294967295 - does anyone have any idea what might have gone wrong there?

Greatful for any advice!
Thanks in advance...