When you scroll down to the bottom of the study you could see things like
White
Black
Termination
Result
Date
Event
I think he meant the PGN is visible there, perhaps by extension of the under board space. (extension from the board?).
It might be the Lichess headers, or LT extension in other panels like sharing, if I recall.
The word extension, I also did not understand, otherwise (I bet wrong English phrasing last sentence. Well. Too late).
