how to calculate manually in the window summary?

Hallo all,

I began to confusion when reading the results capture the data contained in the summary window. The data have been listed on the summary window when it has completed the capture.

Can someone tell me, how the data is obtained?, and how to calculate it manually packet, between lass and first packet, avg. packet / sec, avg. packet size, byte, avg. byte / sec, avg. MBit / sec?

Moreover, how to calculate it manually in the menu Telephony particular delay, jitter, bandwidth, etc.?.

thank you.