I think you're misunderstanding.
Remember, first it checks whether it should spawn a gun or coin.
To do this, I did:
Compare two values 100 < 20 = Spawn Gun
Compare two values 100 > 20 = Spawn Coin
Meaning the coin has a 80% chance of spawning, and the gun has a 20%.
If the value is < 20, we spawn a gun. But which gun? There are 5 guns in the game, so I figured I'd compare another value.
So, if Compare two values 100 < 20, we'll check another value to see which gun it should spawn.
In the event sheet, it'll now look like this:
--- compare two values: if 5 = 1 - Spawn blue gun
--- compare two values: if 5 = 2 - Spawn green gun
--- compare two values: if 5 = 3 - Spawn red gun
--- compare two values: if 5 = 4 - Spawn rainbow gun
--- compare two values: if 5 = 5 - Spawn orange gun
- if value 100 > 20 - Spawn coin.
Hopefully I made sense.
Oh, I'm talking about the compare two values system expression.