Thank you so so much for posting this!
I'm a Dears member too, but my Japanese is too limited to understand it by myself and my friend whom I normally ask about stuff like this is on holiday at the moment >__<

So it's all a lottery, isn't it?
That means, it doesn't matter what time you call, as long as it's in the stated period of time, right?
And the thing that you can only buy four tickets, does that mean four tickets for the same concert or four tickets in total?
And does being able to buy a ticket mean, that you have to buy it?
I'm so confused now >___<

I'd be so thankful for any help, because I totally wanna go! *___*