Hi,
Use below the path and set number ranges for your service master
SPRO ->Material Management -> External Service Management -> Service master -> Define Number Range
Go to menu bar & select - Group -> maintain -> Again Select- Group -> Insert
Go for setting number ranges for your service master
Number Range Group Text 01( For Example)
From Number 9000000
To Number 9999999
and Save.
Now create your service master with t.code AC03 and find the difference!
Regards,
Biju K