I bet tons of people have seen this issue were you have say 500 of one block and you are building a ship, and your need a straight line so you place them fast and use about say 50, but you will have say 470 or so left. after messing around I found out that the blocks don't update fast enough it will actually not register 2-3 blocks if you click fast enough, and vis versa when you delete blocks, so you can lose blocks and gain block by just placing or deleting blocks fast enough.