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Unfortunately I was not able to identify what these icons mean but from what you've shown here I believe we might be able to make some assumptions.
First they are tiny smartphone icons. The white boarder is the edge of the phone, you can see the home button at the bottom of them, and the grey square represents the screen of the phone.
They only seem to appear on icons that make calls or that would open the phone app. So my guess is they indicate icons that were created and/or added by either the phone or contacts app and they will make a call when pressed. I don't know maybe it's a reminder that if you press this icon it will make a call.
If they appear on any other type of app icon this may be wrong so let me know if they appear on any other type of icon, like Facebook, Chrome or Linkedin. Post screenshots if you would to show it in other places.