Custom Alerts doesn't work correctly

I’m currently testing the Custom Alerts plugin for the following situation: I use multiple hostnames, which I also store as custom variables. For each of these hostnames I have created a custom report with the number of visitors I would like to monitor with Custom Alerts.

Now I have the following problem: For testing purposes, I have set for all reports that I would like to be notified if the number of visitors increases by 10% compared to the previous day.

The report from hostname A (1 > 3) appears in the list of triggered alerts, but the report from hostname B ( - > 3) does not.
What could be the problem here or where could I look for the error?