From the Settings screen you can turn on and off each type of notification:
Hotspot Security Alerts
Warns you if you join an insecure hotspot while Speedify is not running. Will only warn you about a given hotspot once per 12 hour period.
Once per day will notify you if you are not connected via Speedify. This is to make sure that you have not forgotten that you have disconnected, and may be insecure.
Dead Hotspot Alerts
Alerts you if you join a Wi-Fi hotspot that does not have access to the Internet. Will only warn you about a given hotspot once per 12 hour period.
The notifications for Cellular being over your set daily or monthly limits are controlled the Cellular Connection settings screen.