The burst rate is the rate at which an appliance can actually send traffic. Many appliances state that they can send traffic at 10Mbps or 100Mbps when in fact this only means that they support 10/100 ehternet connections.
Most of these appliances can not come close to handling 10Mbps throughput for long much less 100Mbps, it is simply un-true.
The Edge appliance is overbuilt for speed. In fact the Edge platform is, one of, if not the fastest performing appliance on the market in its class.