This read-write integer specifies how many bytes into a frame, after the generic media's MAC header, the bridge's 64-byte filter match window begins, with the maximum offset depending on the specific media type in use. An administrator adjusts this to position the fixed-size match window over the relevant part of the frame for whichever media type the generic filter is targeting. For example, on an FDDI port where the header length differs from Ethernet, the admin sets this offset appropriately so the match window lands on the intended payload bytes rather than header bytes.