Approval flow routing to all representatives at same time

Approval flow routing to all representatives at same time even having two representatives in one approval rule set.

Our requirement is second level representative should be able to get approval after the first level approver approves it. But here it is triggering to both approvers at same time.

I am using single type approval set for local and global transfer transactions. There are two rule sets, for first rule set we are having HR Management as one approver representative and other as Human Resource Representative. Our client want this to be routed as first it should trigger to HR Management for approval after they approves it, then Human Resource Representative should be able to approve. But here it is triggering to both approver representatives at same time which is not expected.