What is that Blood Sugar scale?

Hi from Sweden! I've been diagnosed with Type 1 Diabetes for about 14 years, i'm currently 20 years old.

I'm pretty new to this subreddit, and I've never seen the scale used to measure blood sugar, i see 600, 400 etc, according to the scale i use, 4-8 is considered a good level. Is it an American thing like Fahrenheit? :P