Unrated to 1710 in 3 games

I have a friend who has only played three games.  They were against players with the following ratings and in this order (1657,955, and 1063).  He won all three games but I don't understand how his rating went from Unrated to 1710 after those three games.  Can anyone explain how that works?

Thank you CensoredReality.  That makes sense, especially the part about allowing a strong player to reach his "true" rating strength without have to play an inordinate number of games against weak players.  

Your friend may not have started at 1200 like we did.  Pretty sure new members can choose to start as high as 1800.  Your friend probably started at 1500.  Of course Glicko is the main reason, but where you start makes a difference in the beginning.