I have had some experience with ATP devices for verifying production lines being clean etc, however this was a number of years ago.
Id like to demonstrate the value of such a device to a business and have sourced a unit (on loan) to undertake a demonstration.
If i recall correctly high care / high risk environments would usually have pass fail marginal value of around 100 300 500 RLU and low care well i honestly cant recall but was a lot higher...
I have had a play around and have undertaken a full 6 stage clean on a packing table (SS) in high care packing, which is fairly old with many light scratches on but its yielding around 500 ish RLU
I believe i would need to validate the use of ATP machine if i actually purchase te unit which would yield more accurate readings once i have enough data, but would ask anyone that is currently using these devices what sort of target values you are using for each type of area to give me an idea if im in the right ball park.