Price break Header

hi All,

i am facing a litttle confusing when setting modifier for price break header diskon where the event :

customer buy product :

0 - 50 carton, get disc 1% (line 1)

51- 100, get disc  2.5 % (line 2)

101 - 200, get  3 % (line 3)

i have setting but i find that for line 2 the qty cannot input 51, because there is message there is gap ....

and the impact is when i input item for 40 carton then and view adjustment it show 1 % but if i input 50 the system show not even 1 or 2.5 % ?? so i am confusing ..

need ur suggestion or information

thanks

Ef