All I'm getting is ending 4 and its variants :(((((((((((((((((((((((((((((((((((((
Ooh, my bad! The bad ending doesn't have an assigned number since the third ending can be gained depending what "kind" of ending you get (Bad, Good, or True)! So if you've already gotten the True ending per se, the third and last would be the bad ending!
SPOILERS AHEAD!
Select "Leave them be" for both skeletons! Doing this will grant you said ending! :)