I think this is the answer. Just tried this (on free ChatGPT 3.5 though)

Q: A glass door has ‘push’ written on it upside down. Should you push or pull it

A: If the word "push" is written on the glass door upside down, it is likely that the sign is intended for people on the other side of the door. Therefore, if you are approaching the door from the side with the sign, you should pull the door instead of pushing it. However, if there are no other signs or indications on the door or its frame, it may be helpful to observe other people using the door or to try both pushing and pulling to determine the correct method of opening the door.