Volunteer Groups - Allow Leaders to Change the Total Group Members

I would like to know (and if it's not possible, would like to suggest) that you could create a Group but be able to switch up the # of volunteers in the group.

We typically have some of the same groups that come in to volunteer with us, but their # of participants and their # of hours changes based on the opportunity they help with.

For example: We had a group come in this week with 3 people and picked apples on our farm for 2 hours, so that is 6 total volunteer hours for that group. But last month they brought 10 people to pick corn for 3 hours, so that's 30 total volunteer hours for that group.

Right now it seems like I have to create a new group with a different # of participants because I don't have the flexibility to update the # of participants that come for each opportunity and I would like to be able to do that.

Hope that makes sense?