(ii) In cases where gas is supplied to purchasers through orifice or positive meters at other than standard delivery pressure as defined above, a cubic foot of gas shall be defined to be that volume of gas which, at 60 degrees Fahrenheit and at absolute pressure of 14.65 pounds per square inch, occupies 1 cubic foot; except that in cases where a different pressure base that is considered by the commission to be fair and reasonable is provided for in gas sales contracts or in rules or practices of a distributor such different pressure base shall be effective. (Corrections for temperature and pressure shall be made in accordance with Charles' law and Boyle's law respectively, except that, when the meter pressure is 125 pounds per square inch gauge or greater, correction shall be made for deviation from such laws (supercompressibility) in accordance with American gas association gas measurement committee report no. 3, "Orifice Metering of Natural Gas" dated April, 1955, or other procedures which may be approved by the commission.)