[frog in a pot]

Medicare pays 80% of adjusted expenses. The provider puts a dollar figure on the expense. Medicare reduces the amount, then Medicare pays 80% of that reduced amount.

You sound confident, so that may be your experience. For the sake of this discussion, however, the formula you set out doesn't apply across the board.

I'm holding an invoice for blood work just done for a 65+ relative. I'll let you do your own calculations.
Charge: $1137.15
"Insurance Discount": $870.88
Medicare Paid: $140.80
Patient Owes:$125.47

There is no room in there for any element of the formula you state.

[nascarnation]

Having had about a $200 grand in med work the last couple years, yes I have some experience with the Medicare and Medicare supplement systems.