It may be a feeling in review. Glasses represent a cruel learning process, and they are dirty, which means you must be confused and can't see clearly. There are four irregular places that are clean, representing the only knowledge you are familiar with and master.
For example, some questions in the general exam are to be guessed and done, and I don't know if they are right after completion, but some questions will be handy, and you will be able to score after completion, and there is no problem in correcting the exam paper after completion, which represents a very skilled topic.
And this dream means that you may only have four kinds of topics that you are proficient in, and the others are still uncertain. Keep working hard and try to see your glasses clearly next time.