Dung,
This is an interesting situation, but I'm sure PMI has encountered this before. I would therefore recommend that you write to PMI and explain to them what you did on your application, why you did it and what they recommend that you do in regards to the 2 projects for which you didn't include any hours.
I believe that the best course of action for you is to talk to them directly and see what they recommend.
Remember that the audit process is to ensure that you truly qualify to take the exam. If you made an error on the application, then they will help in correcting it or suggesting a way forward for you.