This is a cumulative count of characters received by this specific station since the last node, port, station, or statistics reset. Because it's scoped to one station on a shared multi-drop port rather than the whole port, it lets an admin isolate which device on a shared line has been the heaviest sender historically. For example, comparing CharInTot across all stations on the same port would identify the single device responsible for most of that port's total inbound character volume.