How did jewish scribes check the work done when copies were made of the old testament?

There are a number of steps taken by the Jewish scribes when they made copies of the Old Testament. They have solidified this process by following each step to ensure the that the books in the Old Testament are preserved.

Within 30 days after completing the copy, a review must be made. If corrections are required in as many as 3 pages, the copying process would have to start from scratch. The entire manuscript itself that had these many corrections had to be redone.