[quote=@Suku]
so how are we working legendaries again just by reserving it? cause if we are I would like to reserve Raikou
[/quote]

Basically, you can say a legendary you wanna go for, and it's technically "reserved" for you, but it doesn't mean you're guaranteed to get it. 

It's kind of a placeholder thing, as the nature of pokemon can lead to unexpected results, and it is possible not to catch your preferred legendary or for someone else to. Just a little heads up.