It's best to correct mistakes as soon as possible.
"Ideally, you should fix them right when you find the error."
"Why is that?"
"Because the cost of correction varies."
"Isn't it just about fixing it? Is there a time limit or something?"
"Let's say you're taking a test right now. After completing a question, you feel unsure about your answer. If you immediately correct it and change the wrong answer to the right one, it would only take a moment, right?"
"Yes."
"But if you wait for a few days until the teacher returns the test papers and then make the corrections, the points have already been deducted from your score."