Supposedly, Cheri's story takes place in 20 minutes, assuming the clocks are correct. But from her introduction at 10:54 until 11:14, what we see happens in about 18 minutes. This means that in that extra two minutes, Cheri had time to hook up jumper cables and do a jump, make two car trips and run from her house to the cemetery and back, among other things.
The goof item below may give away important plot points.
When Mark throws the jelly donut at the car Frank is driving, we see it hit the windshield on the driver's side. When the camera angle changes to an inside view, the donut splatter is in the center of the windshield, and when Frank switches on the wipers the majority of the splatter is picked up by the right wiper. After another cut to an outside view, the splatter is back to being mainly smeared around the left wiper.