How does outgoing call work & why two legs?

in cloud telephony, the technical framework is a bit different from your normal day to day calls when you initiate an outbound call from your platform, what actually happens is that two calls are initiated one from the platform to the agent which is called leg a and as soon as the agent picks the call, the second call called leg b is made to the customer both these calls are merged when picked up by both the parties so in an outbound call in cloud telephony, two outbound calls are made from the platform instead of one this results in double usage during a call because minutes are being used on both the calls at the same time hence, if someone made an outbound call of 3 minutes using callerdesk, the minutes used would be 6 minutes in total