No offense but the directions of the test say to hold it tight to the paper (and I have contacted api and they confirmed this) if you don’t it can lead to inaccurate results...
if you read in the instructions it says not to use an “up light” that is where most people have trouble... you need to read it with the tube presses right up against the paper under a light that shines down... again, these are instructions right from api.... if you have anything dark underneath where you are trying to read like a dark table or counter it can make a shadow on the tube and make it hard to read... you need to position yourself so the shadow is not showing on the tube... IF you choose to read it in natural light you must also do so with your back against the sun (or you can once again get false results) if it’s only ammonia you are concerned about seachem makes a product “ammonia alert” it hangs in your tank and ONLY measures free ammonia (not a combination of NH3 and NH4) like the api kit... it is free ammonia that is the toxic one not so much the ammonium... this is why people get confused after using prime... it works by binding the free ammonia and turning it into ammonium (less harmful) however because the api test measures both at the same time you will still get an ammonia reading but your fish are safe because it will detox I believe up to 1ppm of ammonia.... but don’t expect your color to change....
The ammonia one should be very easy to read (if it doesn’t look yellow but it doesn’t look like the .25... it means you are in between) when you have 0 ammonia it is very distinguishable...