Is the tank stocked with fish or are you doing a fishless cycle with ammonia?
What kind of test kit are you using? Strips or drops?
I suspect your test kit is a bit dodgy. Nitrate tests are particularly unreliable. If it is a liquid kit, shake it really, really hard and whack it on a table a few times, then shake it again, then do the test. The chemicals in it can settle and give innaccurate results.
Also make sure you are reading the ammonia one in natural light.
Post a piture of the results against the results chart if you can.