How do I lower playback level?

Hi all
How would I lower the level of an instrument that I am recording? Meaning, lower what I am hearing in the playback mix, Not the recording level!!
I have a stereo mix coming out from my focusrite audio interface…
Into my mixer, (track 7/8 stereo input)
So level would need to be adjusted from within cubase or
Interphase before it reaches mixer…

Any thoughts? Thank you