If you are correctly using the syntax below, little b stands for bits and Big B stands for Bytes. 1KB/sec = 8Kbps.
The real question is if you are having performance problems, or is this a philisophical exercise? If you have performance issues, it’s possible that your AS/400 can’t compute as fast as your network is currently operating. Don’t focus too much on the utilization, unless you’re sure that you’re sending the traffic from the box. If you are, look at Duplex mismatching. Sometimes autonegotiation doesn’t work right and you could be configured at half duplex on one end, which will cause a number of errors.