I don't know if anyone else has mentioned this little trick, but my nitrate level is above what the test kit measures, or even if it isn't, I can't tell thedifference between the top two indicators anyway.
What I do is dilute the water sample by as much as 40-1 with distilled water. Then I do the test. The idea is that the test kit will show readings in an easier range. Then just read off the nitrate level and multiply that value by the dilution factor.