Through STM-1 you can connect 30×63 TDM concurrent calls. But in case of VoIP, this number will be total BW of STM-1 (approx. 150Mbps)divided by per call bandwidth requirement in Mbps.
10K BHCA is basically calculated for switch capacity and STM-1 is channel capacity for sending voice/data. This relationship will vary in case to case basis. In BD scenario, without bandwidth optimization technology and using G.729 codec, you can handle 10K ~ 12K concurrent calls.