Probably this will sound rare, simultaneous calls means they arrive at the same time or be attended at the same time. For a great capacity in a switch means to have power processing plus buffers to queu calls. 1 second is the standard taken to measure capacity for the central processor, some micro seconds are used to attend a call (refer to vendor for your specific case), which means that at the same time just 1 call is attended but within the same second more than one. If your system softswitch handles more processors, means that more than one call could be attended at the same time. Please don get confused processing is different than Traffic, processing has to do with performance or simultaneous events. Thoughs, corrections are welcome