That throught put is always wrong. Monitor the nics and you will see real throughput. I see 3 meg on VPN for 1000 concurrent but in reality it is 50 meg. WHat comes accross the interent pipe is what matters.
The Throughput is indeed shown in KBs. Below is an extract from the Admin Guide mentioning the same,
ThroughputÑThis graph shows the amount of data (in KB) currently being processed._