Number ranges for PM order types

Hi Friends ,

I am defining number ranges for my PM order types but a stange thing is happening . When I am inserting the Group with a number range then this group is not getting added but the number range that i have mentioned for this group is getting assigned to some other group already available in the system like data transfer , internal number range etc.

I am following these steps :

1) Going to Define number ranges in SPRO for order types .

2) Clicking on "Change Groups" .

3) Inster Groups .

4) Entering Group text .

5) Under the Group text , entering from and to number range (not using F4 here directly entering number range which is not created earlier ) (eg 200 to 300) .

6) Clicking on insert button .

Once I am done with above , while assigning the "not assigned" elements to group added above , I found actually the group is not added . But in the overview its showing the number range 200 to 300 assigned to some other group already available in system like data transfer , internal number range etc..

Does nybody know the solution .

REgards