Connor Fauver

It doesn't display the success message in the previous output box because there was no success. There are no creepers with a fuse of 20s. It doesn't decrease.

Thank you.

Actually, if you tested this bug before just brushing me off, it doesn't.
I mean it like this:
Create a scoreboard. Call it whatever. For the sake of this, I will call it "shortFuse"
Run on a /fill clock a command block with the commands

/scoreboard players set @e shortFuse 1 {Fuse:1s}

and

/scoreboard players set @e shortFuse 1 {Fuse:1b}

The first test for entities with the fuse value for creepers, and the second for the fuse value of TNT. They have different labels.

Then run another command block on the same /fill clock running

/execute @e[score_shortFuse_min=1] ~ ~ ~ /say Success

This will have any entity with a shortFuse value of 1 running the /say Success command.

Spawn some creepers. Run at them in survival. I guarantee there will not be a single success.
Create some TNT and set them off. I guarantee there WILL be some successes.

The value of TNT's fuse goes down as it nears explosion, but the value of creepers' does not.