In the scene where Jerry and Trevor are having breakfast, you see Jerry pour Trevor's cereal. When he pours it, the bowl is full. In the next shot, you see the bowl is half full.
Well, I saw this, but what you have to consider is when it cuts to his mother on the phone, he just about has enough time to put the cereal back, because look at where the cereal packet is situated when Jerry puts it down. When we see it after Trevor hangs up, it's changed its position.