While making big ships and using TONS of items (such as power generators/shields)you usually use the 10x10x10 boxes to be faster. alright. when you "spam" clicks the number of blocks in the bar goes down quite rapidly, and it can take a while to stop. If, while the number of the blocks goes down, you switch to another slot of the bar, they duplicate. if you need any more info about this just post a comment here (P.S. sorry for the bad english, I hope you can understand :P)