Serial no. Profile number Range

Dear all,

I have created an equipment category and defined a number range : 1000-1999,this category is assigned to Sr. no. Profile.This Sr. no. Profile is attached to the material master.When a Production Order is created for this material system should create Sr. no. belonging to this range like 1000,1001........,but system is generating Sr. no. like 1,2,3.....Kindly guide if I have missed some settings.