This is a cumulative count of characters transmitted out this port since the last reset, the outbound counterpart to cdx6500allportsCharInTot. An admin compares inbound versus outbound character totals on a given port to spot lopsided traffic patterns, such as a port that receives heavily but sends almost nothing, which can indicate a stuck or misbehaving session. For example, a port with a large CharInTot but a near-zero CharOutTot might indicate a session that's stuck sending data with no acknowledgment traffic going back.