I understand what your on about i do only have single attributes i only deal with different colours.

E.g

If i have a belly bar in 3 colours i.e

6 x red
4 x blue
2 x white

The stock showed up as me having 12 in stock, it allowed me to add 3 white to the cart then when viewing the cart i got an out of stock message.
It doesn't tell the customer i only have 2 white in stock and 6 red etc
Perhaps id done something wrong...