Hypoglycemia

I'm not sure if I'm posting this in the correct area but my doctor is having me test my blood sugar twice a day. I'm new to this and also not a diabetic so I feel really overwhelmed at the information I'm reading online. Unfortunately I didn't ask enough questions while at my doctors office so this is where I'm confused. (They are closed until Monday sadly)

How do I know what is a good range to be in after a meal, when I wake up and when I'm feeling symptoms of hypoglycemia? What I've been reading online is that anything below 140 is normal but how much below is still within the range of normal?

Also added information, the reason why they are having me test my blood sugar for a month is because I had a really really low reading on a non fasting blood test. They brought me in the day after they received my results and asked if I've been having any symptoms. I have been having symptoms but I assumed they were seizure related.