Require help for GCP Stackdriver Log Metric Alert

I need some help. I have a report that generates at 4:30-4:35PM every day with a single log coming in for each one of my 7 reports in GCP.I am using the GCP stackdriver resource which has a custom metric with a report counter and each report can be filtered by its container name which also happens to be its report name. I need to have an alert that triggers if the report is not generated only between 4:30-4:35.

What should I set as its alignment period, evaluation period, muting timings, time range