This secret will be accessible after you help Kate out in the hive on the fourth floor. The reason for this is because once you help Doshi out you will get a screwdriver from him. This tool is necessary for the credit grabbing to work.
Go to the seventh floor and then go into the archive room. From there, head straight down (or north in-game) and walk into the VHS tape room. Follow that handy blood trail all the way up to the closets. Then, go to the left closet (west closet) and open it with your screwdriver. Do this for as long as you want, it’s infinite!