How are the 24h volumes calculated?

Well, I'm mostly interest in Freicoin.
Which of these markets are used?

https://vircurex.com/welcome/index?alt=frc&base=btc&locale=en
http://bter.com/trade/frc_cny
https://www.cryptsy.com/markets/view/39
http://bter.com/trade/frc_btc

Most of the volume seems to be in the first two.