Synchronization between no data alert and the database update

Hi everyone,
I have a problem with graph panel and alerts on Grafana v7.3.3. I would like to do a Graph panel with data stored in a MySQL database, this db is updated every 4 hours, with the insertion of one row. I would like to create an alert rule that inform me when there is no data, but I can’t synchronize the evaluation time interval of the alert rule with the time interval of database update.
My queries are like:
ts AS “time”,
count_da_prendere_in_carico as “value”
FROM monitoring_code_provisioning

I’ve set Evaluate every 4h in my alert rule, and I’ve set 4h in Min interval and Interval in the Query options.

data in the db were like this (“ts” is in utc+00):

but grafana sent no data alert before the 4 hours interval (I am in utc+01)
and I don’t know why.

If I set Evaluate every 5h in the alert rule options maybe I can resolve the problem, but I think this solution isn’t quite accurate, anyone else have other ideas? Thank you!