Hey @NikolaNikola34!
I don’t know if this applies, but the shelf math here will return 0 as the first Z location since 0x35=0.
Next, there’s this. It looks like you’re attaching the Added Mesh to the “Shelf”.
Is the shelf the big column part? Or is it the horizontal piece? Because this could be a confusion point. 
I’m thinking all 3 are spawning they’re just stacking or placed somewhere they shouldn’t be.
Hope this helps get your problem solved!