Explanation:

Box 1: 60
One alert per minute will trigger one email per minute.
Box 2: 12
No more than 1 SMS every 5 minutes can be send, which equals 12 per hour.
Note: Rate limiting is a suspension of notifications that occurs when too many are sent to a particular phone number, email address or device. Rate limiting ensures that alerts are manageable and actionable.
The rate limit thresholds are:
SMS: No more than 1 SMS every 5 minutes.

Voice: No more than 1 Voice call every 5 minutes.

Email: No more than 100 emails in an hour.

Other actions are not rate limited.

References:
https://github.com/MicrosoftDocs/azure-docs/blob/master/articles/monitoring-and-diagnostics/monitoring-overv