Hello Devdath,
You can go to table KNA1. In the selection criteria, give the number range for each Account group and click on Number of entries.
This will give you the number of customers created for that account group. SUbtract this number from the total number to get the Balance.
Note: This is for the number ranges which are externally defined.
For internally defined number ranges, you can simply go to XDN1 and get the balance.
Similarly for Vendors, use table LFA1
I hope this is what you needed.
BR
Amitash