Filter to pull oldest activity associated with a service request

Hello,

I'm building an Activities report and need to pull only the first activity associated with a service request where Type = 'Portal Note' OR Interaction = 'Outbound Call'.

I've already set up the filters on Type and Interaction, but I need help creating the filter for the Start Time, so that it grabs only the first activity associated with any given service request (as long as it's a portal note or an outbound call.)

Thank you in advance!