For example, each item is checked for grammatical correctness. One item can be either a question or a statement. The exam is also checked to make sure every question is supported by a reference. Each answer sheet is put into a scanning machine, which reads the answer sheet and loads all of the information into the computer. If the reference changed and now '4' is the correct answer, I'd change the answer key.
Discrepancies also slow down the process.
Don't sign it if there is something incorrect on it. It's your career. Historically, the No. 1 cause of discrepancies is an incorrect Social Security Number entered on the exam answer sheet. So, people need to double check the information before handing in the exam. The Navy uses a NORM reference scoring system.