Evaluate time trigger mark

What time does grafana service take as a reference time?
Is it system time? Is it start time of grafana-server service?

I’m using version 7.1 (IK, kinda old, but it’s out of my control)

The problem is that my alarm goes off at xx:30 minute mark (8:30, 9:30, …) of the hour, rather than at xx:00 mark as I’d expect.

Is this normal?