If Ammonia is the only test kit your having a problem with, then don't worry about it.
You usually only need to test for ammonia during the initial cycle or when you suspect a major problem. Established tanks seldom have an ammonia issue, unless something really big dies and is not removed.
A reading other than 0 after the initial cycle indicates a problem. You don't usually need to worry about the exact reading. Of course if that reading is off the charts, then you have a huge problem.