Multiple Approvers in a Group
Approval groups are used whether there is one approver or multiple approvers.
1. Substitutes:

Users are registered in an approval group. Sequence No. is 1 for both users if one is a substitute. This means that the approval request is sent to both parties, and as soon as one party approves, the purchase invoice is released.
2. Multiple Approvers Required:

Users are registered in an approval group. Sequence No. is set for each party in the order in which they should approve.
The field "All must approve" is selected so that the purchase invoice will not have the status "Released" until everyone in the approval group has approved the invoice.
If the field "All must approve" is not selected, the purchase invoice will have the status "Released" as soon as one approver has approved the invoice.
You can view how approvals are sequenced on the purchase invoice by opening "Last Approvals".