Apple Watch activity monitor

I would like to be able to change the number of days in my activity cycle. As part of my diabetes program I work in 10 increments but the watch is set for 7 day periods. My preference would be to be able to set it to coincide with the ten day units I monitor my type 2 diabetes with.

For example: To day begins a fresh ten day cycle for me, however, for the watch today is Sunday and therefor the last day of the week. Tomorrow will begin a new seven day week.

If I am stuck with seven day weeks, then I would prefer to be able to select the day I want my activity cycle to begin.

Thanks, Jim