Average on chart with Region Area

Hello,

I have a Line chart with time periods as X Axis, Count of Incidents as Y Axis, and Resolution Code as Region.

Now I want to make one more line on chart - average count of incidents, despite the Resolution code (over all codes).

But when I insert measure like =Average(Count([Number])) on chart, it applies resolution codes to it.

Is there a way to insert a line independent from Region?