This object reports the maximum number of SDI lines that this specific ancillary service has used to carry its data. Some ancillary services, like ones carrying large data payloads, can span multiple lines when a single line's capacity isn't enough, so an admin watching this value climb unexpectedly could be seeing a source pushing more ancillary data volume than usual, which could eventually run into line-capacity limits. A DPI cue-tone service that normally uses 1 line but suddenly reports this object as 3 would suggest an unusually large cue message was inserted, worth checking against the ad-insertion system that generated it.