This read-write integer associates a physical line number with a logical port, with the description noting that on a 4-port AUSM card the line number is identical to the logical port number, but on an 8-port AUSM card the two can differ, implying a more flexible mapping between physical lines and logical ports on the larger card. Admins configure this on 8-port AUSM cards specifically to control which physical line feeds a given logical port, a mapping that's fixed and implicit on the 4-port variant. For example, an admin working on an 8-port AUSM card might need to explicitly set ausmLineNum to associate logical port 3 with physical line 5, a distinction that wouldn't arise at all on a 4-port card.