I've since downloaded a file containing all the 2da files extracted from the game, and the error is in the restduration file from there too. It's just that the rest duration for level 40 appears twice before the rest durations for legendary levels (41-60) appear.
It appears that the error might be in the game files supplied by Beamdog. But like I said, it shouldn't cause problems unless Legendary Levels are someday implemented in the game.
Comments
https://steamcommunity.com/sharedfiles/filedetails/?id=1321231680&searchtext=Rest
https://neverwintervault.org/project/nwn1/hakpak/original-hakpak/super-fast-rest
There's a small error in the file but it won't affect players unless you're on a game which has Legendary Levels implemented as actual character levels.
I submitted that file hahaha!!
It appears that the error might be in the game files supplied by Beamdog. But like I said, it shouldn't cause problems unless Legendary Levels are someday implemented in the game.