If you cut down a tree and it yields a stack of four logs, dragging the logs to your hands will first split the logs into 1 and 3, with only 1 log going to your hands. If you then drag the stack of 3 to your hands, you will take all 3. Attempting to combine them fails. Attempting to drop the stack of 3 logs will result in only 1 log at a time being dropped.