Analyse Survey Tickets in the Ticket Dashboard

Hello all, please excuse my poor English as I'm French. I have set up an NPS survey, with a close the loop program : whenever a client is a detractor, a ticket is generated, and a team calls him back. If needed, the team can create sub-tickets assigned to their colleagues in other departments. I have created a dashboard to monitor volume & status of this process, but I can't manage to separate the "survey tickets" from the "sub-tickets". Eg. : I have 150 detractors to call, so 150 tickets. But my team has created sub-tickets for other depts. And I therefore see "270 tickets" in my dashboard. This doens't help. Has anyone found how to separate external tickets from internal sub-tickets in the dashboards widgets? Thanks for your help Diane