bandwidth limit strangeness

[Mike Cardwell <tor@xxxxxxxxxxxxxxxxxx>]

Hi,

I'm running a tor server called 'Grepular'. At the moment it's a
"partial" exit node in that it only exits a few specific ports. It's
also a directory mirror. I'm running version 0.1.2.13, with this
config:

SocksPort          9050
SocksListenAddress 0.0.0.0
RunAsDaemon 1
DataDirectory /var/lib/tor
ControlPort 9051
BandwidthRate          64KB
BandwidthBurst         64KB
MaxAdvertisedBandwidth 64KB
Nickname grepular
Address tor-node.grepular.com
ORPort 443
ORListenAddress 85.234.136.20:9001
DirPort 80
DirListenAddress 85.234.136.20:9030
ExitPolicy accept *:20-23,accept *:53,accept *:109-115,accept *:123,accept *:143,accept *:389,accept *:465,accept *:587,accept *:636,accept *:989-995,accept *:1080,accept *:6660-6667,reject *:*

I use the following iptables rules to redirect port 80 and 443
connections to the actual ports tor is listening on:

iptables -t nat -A PREROUTING -d 85.234.136.20 -p tcp --dport  80 -j DNAT --to-destination 85.234.136.20:9030
iptables -t nat -A PREROUTING -d 85.234.136.20 -p tcp --dport 443 -j DNAT --to-destination 85.234.136.20:9001

With the bandwidth limits set as they are, why is tor using up nearly
1 Megabit per second? I thought it might be the directory mirror not
being counted in the bandwidth usage, but from googling, I see this
shouldn't be the case?

I have much more spare capacity than 64KB/sec but I'm loathed to
increase the current limits in my config until I'm confident I
can accurately control the usage.

Mike