furnace xp gain is broken - furnace xp faming is broken

furnace xp gain get a higher each time u take an item from it braking the game 

u start with 9 stacks of any metrical lets say cobblestone put them in a normal furnace the with a hopper underneath linked to a chest  output of xp will be the same as smelting 9 stacks and picking them manually 5.4 lvl 

you turn off the hopper so u can take item that will give xp and get the 5 lvl of xp its all narmal until now but u need to add only one block and take it and u will take a full 7 lvl of xp etch time u take 1 block from the furnace

its really a fun killing and removes the excitement of finding a spawned in the the game because u have the op xp sours that u only need to take items from it ones and u got all of the xp in the world  

please fix this .