Invoice approval: 2 approvers must approve from a group of 6

Summary:

I need to find the condition to use in the approval rule spreadsheet that says 2 approvers must approve from a group of 6 approvers. First responder wins but they need to be 2 approving

Content (please ensure you mask any confidential information):

Approval is based on departments. there are approval groups per department with minimum 6 people in each

According to amount limits, 1 or 2 approvers must approve from the group assigned to the department.

For 1 approver it works well. But when we need 2 approvers to approvers it does not work. the 1st approver approves it all

What is the condition to add to the rules?