RULE 8. OVERTIME--OTHER PASSENGER RUNS.     Conductors and brakemen on other passenger runs shall be paid overtime on a speed basis of 20 miles per hour computed continuously from the time required to report for duty until released at the end of last run. Overtime shall be computed on the basis of actual overtime worked or held for duty, except that when the minimum day is paid for the service performed overtime shall not accrue until the expiration of 7 hours and 30 minutes from the time of first reporting for duty.