Weird gui glitch when editing furnaces

when using the block data command if you enter a furnace data like so

{CookTimeTotal:20s,CookTime:1s}

then it will speed up the furnace but if you enter it were the cook time is higher than the total cook time the GUI will freak out for example:

{CookTimeTotal:1s,CookTime:20s}

also there is a picture of what happens to the GUI.