When you get a rejection notice that you're unclear on, just send a message to the editor asking for clarification of the notice. The notice will have the editor's name attached to it. One way of contacting them is to go into QLand and send a note to them though there.
The editors are more than happy to explain the notice in more detail. Please understand that they see MANY quizzes in a day. Because of this, Terry has provided some generic rejection notices for the editors to us. They are very basic ("Please check your spelling and resubmit the quiz" type things) We use these notices quite frequently, because, if we didn't, it would take about 10 times as long to edit.
But, the editors _will_ go into the quiz and give examples of the errors that they are seeing. All you have to do is ask them. They don't know you need more help unless you let them know! 
Just DON'T resubmit the quiz as if you were ignoring the rejection notice. It's the surest way of making the editors look unfavorably on your quiz. You're allowed to disagree with the rejection notice if you feel it's in error, but at least give them the courtesy of communicating that with them.