$SegmentHistoryID :
ID number of history.
$SegmentID :
ID number of your segment.
$Day :
Date in YYYY-MM-DD format
$Count :
Number of items.
$EngagedCount :
$ActiveCount :
$BouncedCount :
$UnsubscribedCount :
Total emails clicked
$AbuseCount :
$InactiveCount :