101 Pa. Code § 13.16
In order to be able readily to find office files of work prepared by the Bureau, bills and resolutions are classified by general subjects in accordance with a schedule established by the Bureau. In writing bills and resolutions, it is the duty of the draftsman to select the most appropriate category and place its number at the top of his draft. If more than one subject seems applicable, the class that has the most restricted scope is used. In amendatory bills, the subject of the amendment governs, not the general subject of the statute amended. The transcriber uses this number on the Bureau folder and on the tracer card. Amendments to bills and conference reports are filed according to bill numbers and require no classification number.
101 Pa. Code § 13.16