Which CYA reading?

[SpaceCoast]

All tests done at waist level.

Facing the sun on a clear day - 60
Facing away from the sun on a clear day - 75
In my bathroom facing the light - 90
In my bathroom away from the light - 90
Outside on a cloudy day - 90

CH - 350 if that helps.

 

[mknauss]

Facing away from the sun on a clear day - 75. Round up to 80

 

[Poolzzz]

Suggest buying the 50ppm Standard from tftestkits for $5 and repeating your experiment. Since it is a known value you will know for sure which is right. Saves all the guessing.