Not sure if this will help, but the AMA's "CPT Changes 2012: An Insider's View" states, "Code 99355 or 99357 is used to report each additional 30 minutes beyond the first hour, depending on the place of service. Either code may also be used to report the final 15-30 minutes of prolonged service on a given date. Prolonged service of less than 15 minutes beyond the first hour or less than 15 minutes beyond the final 30 minutes is not reported separately."