Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,182
It could be trying to say that the cookie it drops on your computer will be valid for 7 days, but only the first booking will qualify for cashback. (hopefully until you click through again)
In any event, Hilton was always terrible at paying out cashback, so I wouldn't get too excited just yet. For one, I'm quite amused about the list of "excluded hotels" excluding a bunch of Las Vegas hotels that aren't Hilton hotels in the first place...