I've found the following and am curious about to why this is.

I copied a piano file to a utility track and Dragged and dropped it and then measured its level using audacity,

The level of the utility track is
-2.9 when BiaB mixer level for the utility track is set to 90(default)

I then did the same measurement of the utility track by dropping the corresponding .wav file (from file folder) directly into audacity and found that it was the same -2.9

In this case a mixer setting of 90 is unity

I then Dragged and dropped and measured the original piano track and found the following

-10.9 when BiaB mixer level for the piano is set to 90(default)

-4.9 when BiaB mixer level for the piano is set to 127(default)

This seems odd and has caused me some problems