help using salifert no3 test kit

[KillerReef]

I have been testing weekly since starting dosing vodka 4 weeks ago with zero change(have been told it may take as many as 8+ weeks. When I tested tonight, I got to thinking, maybe I am reading the kit all wrong.

Should I be putting the test vile on the card and then going by the color on the card that still contrasts with the vile(which would be 50) or go by the color that I can no longer see thru the vile(which is 25)

TIA,
Dave

 

[Josh72836G]

I haven't used that specific Salifert test kit but generally you look through the vial against a white surface and compare that color to the chart. depending on the test kit you may look down through the vial or from the side.