Randomizer isn't randomizing

So basically that's the code ^^

I'm trying to get a 1/3 chance to place one variant of my "ancient bricks" i set the procedure to the first ancient bricks, because it's the block you can get without commands, but it for some reason always places the third ancient bricks variant ,i don't know how to fix this, clearly the randomizer is slightly working but not in the way i expected/intended so, any help on what to change pls?