Ruxandra And Discarding

You have to say how many cards are you discarding when you lock Ruxandra or you can discard and replace one by one until you decide to stop?

Or you have to discard all the cards at the same time and replace them?

Thanks.

Name: Ruxandra
[KoT:V/A1]
Cardtype: Vampire
Clan: Nosferatu
Group: 5
Capacity: 5
Discipline: ani aus OBF
Camarilla: Ventrue get -1 intercept against Ruxandra. You can use a discard phase action and lock her to discard any number of cards.
Artist: Andrew Trabbold

I think it's the latter. You discard whatever number of cards you choose, and draw afterwards.