using /blockdata command to set dispenser to have tnt amount to negative value will fire 1 tnt and set the item count to 0

using /blockdata command to set dispenser to have tnt amount to negative value will fire 1 tnt and set the amount of item to 0

(I'm not sure about other item fire out of dispenser , but this problem isfound when I want to use my trap)

What I expected to happen was...:
using /blockdata command to set dispenser to have tnt amount to negative value will continue to fire tnt and set the amount from item to -2,-3,-4,...
using /blockdata command to set dispenser to have tnt amount to negative value will fire 1 tnt and set the amount of item to 0

how to reproduce it:
step 1: make a new world (cheat is enabled!) or just use your world that have cheat enabled
step 2: set a dispenser
step 3: made a very fast clock and wire it to dispenser (not a command block clock one-that will be too fast so the dispenser can shoot once)
step 4: stop the clock
step 5: set on the dispenser and type following command

/blockdata ~ ~-1 ~ {Items:[0:

{slot:0b,id:"minecraft:tnt",Count:-1b}

],id:"trap",Lock:""}

or just copy it from cmd.txt file (it's the command to set the tnt in 1st slot to -1 , I'm not sure about other slot)

step 6: start the clock and you will see the problems

test if it occur to all negative value :
in step 5 change command from
/blockdata ~ ~-1 ~ {Items:[0:

{slot:0b,id:"minecraft:tnt",Count:-1b}

],id:"trap",Lock:""}

to

/blockdata ~ ~-1 ~ {Items:[0:

{slot:0b,id:"minecraft:tnt",Count:<other negative integer>b}

],id:"trap",Lock:""}

(be sure to change the <other negative integer> to negative integer!)

or you can copy 2nd command from cmd2.txt

(again ,be sure to change the <other negative integer> to negative integer!)