Memo on the Pass Number

Find the four-digit pass number for the biology experiment room emergency lock system in Resident Evil Code: Veronica X, located on a skeleton picture.

The emergency lock system in the biology experiment room can be released with a four-digit pass number. The system administrator requests that the pass number be changed periodically. To solve the problem of losing important memos or pass numbers, the number signed on the red human skeleton picture at the back of the biology experiment room is used as the pass number.