Reporting API: Zendesk-style Ticket Volume vs GC Interaction Count

Does anyone know how to align Zendesk ticket volume metrics with Genesys Cloud interaction counts in the Analytics API? Our migration dashboard shows a 15% discrepancy. In Zendesk, a reopened ticket counted as new, but GC seems to group these. I am using the /api/v2/analytics/conversations/details/query endpoint with interval=day. Here is the payload:

{
 "dateFrom": "2023-10-01T00:00:00.000Z",
 "dateTo": "2023-10-31T23:59:59.999Z",
 "filters": {
 "interactionType": "message"
 }
}

How do I filter for unique customers instead of total interactions?