the charge proportion (as defined in clause (ii)(II)) of 62 percent (for services described in subsection (a)(2)(E)(i)), or (for procedures described in subsection (a)(2)(E)(ii)), 42 percent or such other percent established by the Secretary (or carriers acting pursuant to guidelines issued by the Secretary) based on prevailing charges established with actual charge data, of the prevailing charge or (for services described in subsection (a)(2)(E)(i) furnished on or after April 1, 1989 and for services described in subsection (a)(2)(E)(ii) furnished on or after January 1, 1992 ) the fee schedule amount established for participating physicians for the same services as if they were furnished in a physician’s office in the same locality as determined under section 1395u(b) of this title (or, in the case of services furnished on or after January 1, 1992 , under section 1395w–4 of this title ), less the amount a provider may charge as described in clause (ii) of section 1395cc(a)(2)(A) of this title .