I know for sure there is something to the dim line versus a dark line. I've used the same test and watched it go both ways. I don't think these tests are so sensitive to detect the difference between 49.9ng and 50.1 ng. So the difference in color MUST have something to do with the level if not a complete quantitative reading.
As youve been informed in your own thread (in which the topic itself needs to remain in that thread, rather than highjacking other threads), if this was actually true, then
synthetic urine controls wouldnt be producing faint lines on any drug assay.
Again, a negative is a negative. Youre worrying yourself over nothing.

I don't think any of these guys who say "a line is a line" would want their employer seeing a line that is barely visible.
Uhh..I wouldnt want my employer conduct any of my U/A's, let alone see if the U/A has a line. Thats because my employer is not certified & authorized by the DHHS to collect and analyze samples.

And more likely than not, yours isnt either. Thats the job of the facility.