I have an Azure Function that every 4 hours runs a database query and writes logs to app insights in case of errors found.
I create an Azure Alert rule with this query:

union traces, exceptions
| where message startswith "Reconciliation error" or message startswith "Reconciliation check failed"

Intention is: trigger every 4h, query last 5 hours, and if anything is there, raise alert.

Setting Alert rule granularity: 5h and Frequency of evaluation: 4h means there will be a sliding window, but I just want to run this every 4 hours.
Is it possible to achieve hopping window functionality instead?

Note: This docs page metnions a Lookback period “Select how far back to look each time the data is checked. For example, every 1 minute, look back 5 minutes.”
but I dont see any such option in the portal