Episode 7 gave us the BIG answer. [E7 spoilers]

They’re preparing to mass market Severance. You have the chip put in and can sever yourself from all unpleasurable experiences in life. You can just send an innie.

Currently, that seems to be available for the incredibly wealthy elites in the birthing cabins but soon, you can use it for the dentist or going to the gym, or possibly much worse things.

Each file they’re working on is code named for one of those experiences that train the software in the chip to balance the tempers when they exit the room. Allentown was dental which is a completed file, and Gemma did not feel anything other than her sore jaw because the file is complete. I’d have to check the timeline but 6 weeks ago actually might time to when Mark closed that file.

My much bigger swing is I think Cold Harbour is going to be loss - you can actually sever the memory of losing someone. When Mark completes that file, Gemma will go through the Cold Harbour door and not remember Mark but stay as Gemma.