In Stanley's first scene, the computer wakes him reciting his Number as 4-7-6-3-2-9-4-3. Thereafter his Number is recited and written as 4-6-7-3-2-9-4-3.
When Stanley visits security pretending to be someone else in order to find out what his punishment will be, the guard looks up his file in order to determine the punishment. Later on it is shown that these files have photos attached, meaning the guard should have known who Stanley was and apprehended him.