Queue Performance SLA Breach Calculation Logic in EU-West

Can’t quite understand why the Queue Performance view in EU-West calculates Service Level as 85% when the Architect flow logs show a 20-second wait for calls answered within the 15-second SLA threshold. The standard metric definition suggests a breach, yet the dashboard aggregates this as a success. Is there a specific rounding or buffering mechanism applied to the timestamp capture in the performance views that overrides the raw flow data?