(a) Tariffs covering each kind of public service shall be numbered consecutively, in the order of their filing dates and the tariff designation shall show the kind of service and serial number as follows: ‘‘Electric Pa. P.U.C. No.

.’’

(b) Supplements to tariffs shall be numbered in the same manner, as follows: ‘‘Supp. No.

to Electric Pa. P.U.C. No. .’’