This object reports the line number where this specific ancillary service is expected to be found in the SDI signal, based on standard convention or configuration. An admin comparing this expected line against the actual line reported by vancServiceStatusACTLineF1 or F2 can spot a source that's placing its ancillary data on a non-standard line, which some downstream equipment might not correctly read even though this device does. If this object says line 9 for AFD but the actual reported line differs, an admin would flag the upstream source equipment as using a nonstandard line placement, useful context if a different downstream device later fails to read that same service.