Club Distance Average change

I am new to Garmin, and i have searched this forum but i couldn't find the answer.

I have the Garmin S70 with the CT10's

With regards to Club Distance Average, does the average come from ALL your shots per club/round, or from the last 20 shots per club/round.

As I'm a new golfer, and the change of weather conditions, my club yardages will change, what i don't want, is that Garmin takes my worse/shortest shot from 6 months ago, in the wind and the rain, and take my improving shot when  getting better in good weather, as surely, that average would be incorrect due to current skill level.

Or, do i just have to delete, re add a whole bag when the weather get better and my handicap does.

thanks in advance all