MW is right. Liquid color matching tests have no meaning other than your interpretation at the correct time. Always ignore a color interpretation at any other clock time. This is what the test designer has designed for.
Your confusion sounds mostly to be just another variation of needing to be patient. This is not a chemistry process. Its biological and the readings you're taking are very "second hand" from the process taking place, so things will jump around. Your job is just to make a reasonable interpretation of the color and record it in your log and then periodically study the -trends- and discuss here. A trend will mean more than any one reading.
And yes, -zero- readings, especially with the API kit will be quite clear when they happen!
~~waterdrop~~