You're saying a 7 day rental is $500 but an 8 day rental is only $250? Are you sure?
Anyway, if you don't meet the terms of your rate quote, the rate will nearly always revert to what you qualified for...in this case...the 7 day rental. And it likely will not be the same 7 day rate you're seeing now.
Book accurately but don't prepay anything. Continue to monitor rates and they likely will come down anyway unless some huge event is taking place in that locale. Continue to make new bookings and cancel existing bookings as you see the rates drop.
BobK/Orlando