Okay, I'll walk you through how it works...
!deaths gives you the total counter, it's just text
!deathadd adds a death to it's internal counter and edits !deaths
!deathreset resets the !deathadd internal counter to 0
So here are responses from the bot:
USER: !deaths
Nightbot: Channel has died 0 times playing game
MODERATOR: !deathadd
Nightbot: !deaths has been edited — !deathadd internal counter = 1
USER: !deaths
Nightbot: Channel has died 1 times playing game
MODERATOR: !deathadd
Nightbot: !deaths has been edited — !deathadd internal counter = 2
MODERATOR: !deathadd
Nightbot: !deaths has been edited — !deathadd internal counter = 3
USER: !deaths
Nightbot: Channel has died 3 times playing game
MODERATOR: !deathreset
Nightbot: !deathadd has been edited — !deathadd internal counter = 0
USER: !deaths — !deaths hasn't been edited yet, only !deathadd edits it
Nightbot: Channel has died 3 times playing game
MODERATOR: !deathadd
Nightbot: !deaths has been edited — !deathadd internal counter = 1
USER: !deaths
Nightbot: Channel has died 1 times playing game