This object indicates whether this specific input source became the currently-selected clock as a result of an operator-forced switch, the per-source-table view corresponding to what cnsSelInpSrcFSW reports for whichever source currently holds T0. It matters when reviewing the full candidate list to understand not just which source is active, but whether its selection is a result of an override that a colleague may have applied and possibly forgotten to remove. Cross-referencing this being true on a source with a lower QL than another available source confirms a forced override, not the normal algorithm, put that lower-quality source in charge.