@FireMonkey
The $189 is the amount the Dr charged. That amount is before medicare looks at it.
The $159 is the max amount Medicare approved, whis is usually the average of what Dr's charge in your area.
Medicare Part B (which covers Drs bills, only pays 80% of what is approved. 20% is what your supplemental insurance is responsible for. So $153.23 − 80%= $30.54
Of $30.54 your supplemental/private ins PLAN COST covered $20. The $10.65 you pay. Your ins uses different reimbursement tables
@FireMonkey
What did they charge you for, labs, x-rays? You should reach out and ask the doc for a detailed statement of charges for your visit.