If something is 200% greater, it means that it's more than something else by 200%.
You often hear stuff like, "Attendance was up by 50%" or something, which is similar.
Let's say one day, 1000 students come to school.
The next day, attendance goes up by 50%.
You take 50% of 1000 (500) and add it to 1000
1500.
If attendance went up by 200% (from 1000), you'd do the same thing.
Take 200% of 1000 (2000) and add it to 1000.
3000.
It's generally used to say how much more something is than something else.
