VvV Altars and how they work?

[S_S]

I'm not fully getting how these work.
I understand when an opposing player steps on it, the flames start over.
I don't understand how it works when I stand on one, get 85-90% through the flame circle and an allied player runs up and stands on it for 2 secs and claims it?
Yet when I tried that on them, they still claim it?
I'm missing something again aren't I?

 

[SpyderBite]

If you're in the same guild, or your guilds are allied then you should both get credit for the claim.