[tor-relays] Raspberry pi 3 relay performace

Hello everyone, I have a tor relay running on a raspberry with raspbian 9 and tor version 3.4.8, everything is working fine for more then a year. I noticed that the average download/upload is just 1.5 MB and the peak 3.3 MB

The Bandwidth configuration is the following: BandwidthRate 9 MB BandwidthBurst 10 MB RelayBandwidthRate 9 MB RelayBandwidthBurst 10 MB MaxAdvertisedBandwidth 9 MB

It doesn't look the CPU or memory usage are too high. Is this something normal? How can I improve the performance?

Thanks a lot