Different banks do this differently. You'll need to look at the oto configuration for the voicebank to see how it's handled specifically.
Most overseas and some native japanese banks will label the breaths as br1, br2, etc, with no other indication of what it is. Others will use kanji and other symbols.
When placing these notes, I suggest editing the note properties and setting the modulation to 100.
Alternatively, if the breaths are by themselves and not an end-breath, you can place the breath samples down while mixing. That way you don't have to worry about the breaths losing quality when going through UTAU.