They send you an email once you've qualified (as long as you've paid the 3 months).
So if you haven't gotten the email it's probably 2 months only
Also like ferey said the legacy logo will appear in character select screen
My gf came back from a trip to the USA today and reactivated her char for 90 days at 16:30 local time which equals to 23:30 JST. Now the 90 day subscription option is gone. Let's see what happens about the legacy status.
For me, it took a couple of days for either the icon or the email to show up, so if you signed up for the 90 day option and don't see it yet I wouldn't be too worried.
I think I'm screwed because I had some extra Crysta left and paid for a month on June 9th or so when I reactivated. Then when I found out about Legacy, I changed my option to 90-day, but it says that it won't start until July 9th which is after the deadline. I would have gladly paid the 90-day for it but I didn't know about it when I first reactivated.
You will qualify for legacy if you've paid for 90 days total between January and the start of the beta. That means if you paid for a month starting in June, you can still buy two more months, it just won't be in one payment. You won't be notified until the billing cycle in which you pay for the 3rd month.