Combo Ticket For Xian Sightseeing Bus + Wall

The bus ticket is good for a 24-hr timeframe. Do I have to see the wall during that same 24 hrs if I buy the bus+wall combo ticket? Or can I see the wall in a different 24 hrs? If it's the same 24 hrs it would mean I wouldn't get to see many of the other spots other than atop the wall. Has anyone bought this combo ticket?