Monthly Analysis - add an average column?

Hi,

in the template sheet “Monthly Analysis” I have my months in columns B to M. That’s the regular stuff and I like it quite well like that.

The one thing I would like to add but I am not sure if it will break something (I am new to Tiller), is an average for these 12 months. I would like to insert between columns A and B, from row 25 (below the graph), an average that will help me budget better.

If I do add something between current columns A & B, but below row 25, will that break anything?

Many thanks,
BDR