It's actually 7 days in a 30 day window. There are signs posted indicating such at the entrances.

All Army Corps camping is limited to 14 days in any 30 day period. Boondocker's Bible has a good discussion on this... https://www.boondockersbible.com/knowledgebase/how-long-can-you-camp-at-an-army-corps-of-engineers-campground/