Gatp is happening only at particular quantity level

Dear expert

Gatp is hapening only at particular level  quantity like 6000 when i am giving quantity above 6000 it is not happening .we generally go gatp with avilabilty check do we mantain any restriction at quantity level .As we are using ppds block planning is very fine i.e block is for month and with huge capacity in /sapapo/cdps_rept .

Thanks in advance

Regards

Virender.s