ISO 4406 Cleanliness rating

Mine never seems to move. There are three lines running about a right angle, the rating I guess is 20/17 The top number is 5000 The bottom is ~650 anyone have anything different? Can a system be cleaner? Even when I ran a By-pass, my numbers only changed a couple times... As I figure it, since they never change, it must be like the Water and Fuel... at a set limit, and whenever a FLAG is triggered, then they look into it>>>>> What would trigger the lab to run a REAL test?