Hi Aamir,
There is no easy out here. My take is that you are incorrectly notify group manager for everything. So you need to check ALL the SLA notifications configured and figure out where it is necessary to send the notifications to the group manager. Wherever you wish not to be notified, simply remove the Group Manager.
You could even go to the extend of adding a macro to check the group on the ticket and then only send out the relevant notifications when the group matches one of those you are the group manager for.
This should help reduce the amount of notifications you sent.
Kind Regards,
Brian