What is this number on my clip header ?

That clip is part of a "Selection Group."  You can select all of the clips with that number and right click one.  Choose "Remove Selected Clips from Groups."

You must have create clip groups checked in recording preferences.

There's also a setting there that controls how grouped clips behave when you split them. They'll either become part of their own new group or stay in the current one. If it's the new group option the groups soon stack up.

HTH

Sorry that's what I get for working from memory..... The split clip grouping option is in Prefs-->Customization-->editing.

You'll get a new group everytime you press record or at loop start. Every split you make will create a new group as well assuming you have theat option checked.

It's not user changeable as such. It's a number assigned by Sonar to indicate the group number it belongs to and AFAIK are assigned sequentially as clips are grouped.

To ungroup select one of the clips, right click and select "remove selected clips from group" which effectively ends the group as all clips in it will be selected.

Create them by selecting all the clips you want in the group and selecting "create selection group from selected clips". A clip can only belong to one group at once though.

For example if you have 3 clips in group 1 and two in group 2, select them and then "Create group from...." you will create group 3 but groups 1 & 2 no longer exist.

Hope that makes sense.