Hi Deepak,
If You fill exam form for both groups and appear only Group II, if you cleard group II then you will be counted in group II as appeared & successful. And if unfortunately the group II not cleard then it will be counted in both groups.
thats why Both group result is always less as compare to Single group.
Because Passing Both group all the subject is not easy for many candidates so before exam many candidates shift to single group so as to secure at least one group.
And those who have fill the form for single group then they will be counted in there respective group.
Only from both group applied candidates those who succed in any one group will be counted in that respective group and those who not succeed any one group will be counted in both group .
hopefully you might have got clarity on your doubt.
Thanks & Regards.