If they are holding 20 tickets, then it is not subject to availability.
The press release ALSO listed the two specific dates that tickets will not be available. So then why say that "tickets may not be available for all performances"? Either 20 tickets are available for all performances, except the two they specifically mention, or they are not.
Nothing matters but knowing nothing matters. ~ Wicked
Everything in life is only for now. ~ Avenue Q
There is no future, there is no past. I live this moment as my last. ~ Rent
"He's a tramp, but I love him."