Here's what I got for a 7 day vs. and 8 day rental using contractID found at 
Travel Coupons Online and a Delta coupon. Interesting difference in how they compute rates and discounts.
7 Day rental
Time & Distance 1 Week @ 147.23 147.23   
 Extra - Time & Distance 0 Day @ 24.54 0.00   
 Extra - Time & Distance 0 Hour @ 12.27 0.00   
 Unlimited Distance-time & Distance 0 Distance @ 0.00 0.00   
    
Base Rate ___________
147.23   
         
  Less Discounts:     
  Csa -delta 5/01 Insert  -20.00   
   
SubTotal ___________
127.23
   
          
  Add Surcharges & Taxes:   (subject to change)   
  Concession Fee Recov Chrg 9.8 Pct 14.43   
  Fl Schrg/tire&bat Fee 2.05 Usd/dy 14.35   
  Fla License Fee .41 Usd/day 2.87   
  State Tax (6.0%) 9.53   
Fftxrsu (0.0%) 0.42   
   
Total Estimate ___________
168.83
8 day rental 
 Time & Distance 1 Week @ 151.99 151.99   
 Extra - Time & Distance 1 Day @ 25.33 25.33   
 Extra - Time & Distance 0 Hour @ 12.67 0.00   
 Unlimited Distance-time & Distance 0 Distance @ 0.00 0.00   
    
Base Rate ___________
177.32   
         
  Less Discounts:     
  Discount  -17.73   
  Csa -delta 5/01 Insert  -20.00   
   
SubTotal ___________
139.59
   
          
  Add Surcharges & Taxes:   (subject to change)   
  Concession Fee Recov Chrg 9.8 Pct 15.64   
  Fl Schrg/tire&bat Fee 2.05 Usd/dy 16.40   
  Fla License Fee .41 Usd/day 3.28   
  State Tax (6.0%) 10.49   
  Fftxrsu (0.0%) 0.48   
   
Total Estimate ___________
185.88