Non-priority texts getting through when downtime is set for only priority contacts.

[AC Question]

I have my phone set to priority interruptions only from 10PM to 7:15AM - for phone calls and texts from starred contacts.
I keep getting alerts for texts which are not from my two starred contacts. Usually it has been from short numbers - such as 5 digit bank alerts, but today it was from someone in my contacts who is not priority (no star).

Nexus 5
Android 5.1.1