[tor-relays] Relay bandwidth

I have configured Tor with the following (with daily accounting):

RelayBandwidthRate 384 KB RelayBandwidthBurst 512 KB

I always assumed that the burst bandwidth will set the maximum relay bandwidth. However, by using iftop, I can see individual connections with speeds as high as 2+ Mbps. Even when individual connections are not exceeding burst speeds, adding up bandwidth of all connections would probably exceed allowed relay burst bandwidth.

Is this because Tor is using up the bandwidth allowance, since it is well below its long-time average or is this something unexpected that should not be happening?