Grading Raw power is very much a distance thing. How far can someone hit a baseball. Can see it in BP or in games.
Grading Power is very much a frequency thing. Based on true HR distances. Need to see it in games against good pitching.
So it is possible to have an 8 Raw power grade and a 5 Power grade.
Gap power adds to the hitting grade.
This is why scouts want to see BP. Then see the games.