Medicare Statement for Remicade charges

My last Medicare statement for my last Remicade infusion is as follows:

Total amount charged:     $13,256                                                      Medicare approved:           $13,256

Medicare paid provider      $156

Amount you may be billed  $40

I really don't understand this.  Medicare approves a payment of  $13,256 and then only pays the hospital $159. I'm glad I only have to pay the hospital $40 but

I don't think the hospital is going to do Remicade infusions if they only get paid $196 (156+40).  I sure I'm missing something.  Could someone help me out please?

By the way,  this was my fifth infusion and Remicade has done wonders for me.  I am symptom free.  I hope it lasts.

Yea this is strange to me also,I often wonder how medicare does not have enough funds,they pay less than 10 cents on the dollar,or in the OP's case almost nothing. Wife went to ER,10K bill for six hours, wifes medicare advantage paid $746,I paid 50. Wife even had a CAT scan and I know that cost more than 746. Don't understand at all how the payout system works.
Old Mike