Number Clicking

I was putting my blocks/items in the hotkeys.. i misplaced the item and i do the number click (example: place the cursor in the item then press 1)

What I expected to happen was...:
It changed the items/blocks

What actually happened was...:
It actually change the picture.. but if you place it the block will be the block again.(I place my cursor in the dispenser which it is in hotkey number 2 and then press number 1. Now the dispenser is in the hotkey number 1 but if you place it, the block that you exchange with it,is the one you place)