The number is a reading of your glucose in ml/DL.

Consult with your doctor on what's "good" for you.
Testing before eating, and then a few hours after eating will be a good thing to do.

Everybody is different, but commonly any number <60 is BAD and indicates a "low blood sugar" condition.   What would be determined as "High" for you is something you should talk to your doctor about.   (for me it's anything above 150, but for my brother, he was told above 120).