Might seem like a silly question but when you read the results of the test, do you hold the tube fully against the white background (touching the tube to the paper) or do you hold it just in front of the white background? Because for example when I’m checking my nitrates, if I hold it against the paper it reads more like 10-20ppm but if I hold it just in front of it (not actually touching the tube to the paper) then it reads 5ppm. Just wasn’t sure which one is the more accurate reading. Any thoughts? Thanks!