This is the byte-level counterpart to cktInFrames, giving the admin the actual data volume received on this circuit rather than just a frame count, which is what's typically used for accurate throughput and billing calculations. For example, dividing the delta in cktInOctets between two polls by the elapsed time in seconds gives the circuit's actual inbound throughput in bytes/sec, which the admin compares against cktCir to see if the customer is running near, at, or over their committed rate.