Assuming no other entities on the bus, and nobody hanging body parts outside, and the requisite 2 leg girls and 4 leg cats...

Each big cat maintains 7 small cats, for 8 cats per big, inclusive.
Each bag has 7 big cats, for 56 cats total.
Each girl has 7 bags, for 392 cats in total.
392*4=1568 cat legs, +2 legs for the girl, is 1570 legs per girl system.

Seven girls makes that 10990.