Pro tools Master level is -12 dB Below from aux output

[UnSoNiC]

Hello,

I have a problem with pro tools tdm. When the level of my sine generator on an aux track or audio track is set at 0db with the fader of this track at 0 db i should have 0 db at the master output but i have -12db.
And when i create an aux track, everything that is sent to this aux track is -18 db below if sent post fader and -12 db below if sent pre fader.
What's the problem?
Thank you