Cancelled line amount for PO approval

Here is the scenario

Approver 1: limit 1-100

Approver 2: Limit 100+

1. PO # created for $150.

• PO # approved by Approver 1 and Approver2
• Received and Paid for $110
• PO # cancelled for the remainder amount

1. Change order added for $5

• The PO # gets approved once the Approver 1 has
  approved the request

Question: It should have been approved by both Approver 1 and Approver 2 .
Since the total amount F4301.OTOT is $115. But it got approved once the Approver 1 approved the PO.  Is this correct.