Reporting order tags quantity

I have just noticed T.Qty.Sum doesnt seem to respect the qty of the order its tagging.
ie.

2x Order

  • Tag

The above only reports 1 tag for quantity sum but the above is 2 of whatever the tag is in same way if was double tag the T.Qty.Sum would report 2 when it should be 4 since there are 2 qty orders…

Am I missing something?