[Ardour-Users] Peak levels on master bus vs single track

[Alf Haakon Pietruszka Lund]

I just finished a project in Ardour 4.7.0 on Ubuntu Studio 14.04

There are several regions in many tracks, some of them overlapping in 
time, most of them not.

On most of the tracks I used a compressor and a limiter (both from calf) 
to avoid peaks and potential clipping. I set the limiter's output gain 
to minus 2.2 dB.

As expected, when focused on one of the tracks, the meter doesn't pass 
-2.2 dB.

However, when focused on the master bus, the meter 'clips' and peaks at 
+0.9 dB.

Why is this? Will it affect export and normalizing of the project? If 
yes, how?

Thankful for any and all input,
Al F