They are allowing the amount that they allow for a procedure performed in an ambulatory surgery center. They allow less since the provider who performed the procedure did not have the overhead costs of an office, staff, etc. So even if the dr is not employed by the center, if he/she comes to the center for perform a procedure he/she didn't have the cost of the facility. I don't believe that a modifier, or an appeal is going to change anything.
Did I totally miss this question??