For example. My local water report states that the tap ammonia in my area is 0.5ppm. But it reads from my test kits as 0. Nitrite is given as being 0.5 but this also tests at 0ppm. Nitrate is given as being 50ppm! Now bearing in mind my test reads it as 0ppm from the tap that's a huge discrepancy!
Are you sure the report really does say that? Mine used to give a list of substances with the measured level in one column and the maximum allowed level in the next. Now they only give the max allowed levels. Is your water company doing what mine has just started, and only giving the max allowed levels on their website? That's what the figures you give are - the max allowed levels.
My water company also used to have a pdf with harness, pH and alkalinity listed for each town. That's gone too. Now it's just the hardness when you type in your postcode.
You are right, I misread it. Those are the maximums. LOL what an idiot!

I blame trying to read the report and type about it with a tired screaming baby on my knee!
However, it does give the number of tests done, the maximum readings, minimum readings and the means for each. I wonder why yours doesn't

I did have to download the full report to be able to get those readings: the website only gives a few of them, and ammonia is not one of the ones listed on the site.
Ammonia - 52 tests
Min: 0.01, Max: 0.02, Mean: 0.0112
Nitrite - 8 tests
Min: 0.0052, Max: 0.0093, Mean: 0.0083
Nitrate - 8 tests
Min: 1.3305, Max: 2.6572, Mean: 1.9064
I don't feel nearly so bad about dosing 30ppm nitrate now

can't find anything about phosphates though.
And, while my tests do now seem more accurate than I originally said they were, my point is still valid though. The test kits can't be very accurate because of their presentation and usage. Plastic bottles of reagent, used on water from a tank where all the environmental variables cannot possibly be allowed for and controlled, in a test tube that is probably still tainted from the last test. Plus there's human error when actaully doing the tests to take into account. I've miscounted drops so many times I can't remember. There's always going to be a certain amount of uncertainty.