ph levels can hide ammonia in the form of ammonium
ammonia test kits test ammonia (not ammonium)
and the chemical swings back and forth as the pH rises or lowers
under 6.5 about (i don't remember exactly), it's almost all ammonium
at about 9.5 it's about 50/50
not sure what test kit you have
i'm not sure how they all work, i only know from my own kit
it's a chart, "your color is X" "what is your pH level in your tank?"
you look at the chart, take the ammonia reading, line it up with the column for your tanks pH, ... and this will tell you if things are dangerous or safe or whatever.
because of that pH thing it makes testing ammonia ... not exactly easy, it's a ratio.
as i said, i don't know much about test kits, ... but ... that random thought i had, ... if your test kit raises the ph to detect more ammonia ... ... the test kit could be reading a higher level of ammonia then what your fish are experiencing in the tank.
have a look through your test kit manual/booklet/sheet/whatever to see how to read the results of your test.
somewhere it's bound to say what it is doing or what to expect, or what's dangerous or whatever else is going on, going to take some reading of your test kits instructions.
at this point worry less about the 0.25 reading, and look through the instructions to see what that means.