Not necessarily. You can claim a second prompt after your first entry has been submitted.
And how is the claiming achieved?
Claims will be open on the 22. And it is first come, first served. We hope to have enough variety for everyone to find a good match. Each prompt can be claimed up to four times - 2 times for authors, and 2 times for artists. We want everyone who wants to participate to have a chance to do so. We've put some restrictions on claims to give as many bunnies as possible a chance for adoption and to have as much variety as possible in the fest. But, if you really, really, have your heart set on one prompt and it has already been claimed twice, please e-mail the mods.