Tauri,
Got the response from Aqueon. As expected:
"Hi John,
That sticker means at least one of the panels is tempered. The only way to determine if the panel you’d like to drill is tempered would be to check with a polarized lens. There are some videos on You Tube that will show you how."
Doughboy,
Here are two links. First one you have to watch for a while till the picture shows up:
https://www.youtube.com/watch?v=cYW6iGUFnS0
https://www.youtube.com/watch?v=O3J47iP1KKM