Well underneath the bag it does say how many slots are there...wait you mean bags on the ground (I assume...bit too early still). In which case I might suggest it lists the number of taken slots like the inventory ones do; when I saw the example I thought it meant two slots were filled.
Guessing you mean dropped bags as well. Perhaps, rename/amend the bag name to reflect the number of spaces left? Your suggestion would be useful in any case.