Thread: Screw sizes

This is a really simple question, but one which google has not been able to answer.

I'm normally very familiar with screw gauges, and on the weekend I went down to bunnings to pick up some 8g and 10g chipboard screws which I'd run out of.

However, instead of the usual boxes of "8g x 65mm" and "10g x 75mm" screws, bunnings now stocks boxes of what are labelled "8-10 x 65mm" and "10-8 x 75mm".

Now I've assumed (just by eye) that the "8-10" are 8g screws, and the "10-8" are 10g screws, but I can't for the life of me figure out what the extra numbers are for.

Anyone have any idea? (other than stupid bunnings labelling).