Two number ranges in a group

Hello,

I am trying to add a second number range into a group, but i can't do!

Here is my problem in detail:

i have number range 490000 - 719999 for material type 2000, and

number range 420000 - 449999 for material type 3000, in the corresponding groups.

I want to add the range 500000 - 509999 into the group with material type 3000.

So i have to brake the first one in two ranges :

1st : 490000 - 499999

2nd: 510000 - 719999.

Is this possible ?

and what steps should i follow to make this change ?

Thanks in advance.