The NADA (National Auto Dealers Association) guide is a "guide" that gives you an estimated assessment of what a vehicle is worth given the condition that the vehicle is in. This is not a definite value of what the vehicle is worth. This value should not be confused with "fair market value."
There are also two types of NADA Guides. One that is used by the consumer, the end purchaser; and another that is used by banks, auto dealers and insurance companies. This should stand to no surprise. What a used car dealer would expect to purchase the same vehicle at, is much different than what a consumer would. Don't get these two confused.
The NADA breaks down the pricing into three categories based on the information that you provided such as option and overall condition.
The first category is Low Retail. Low retail means that the person who purchases a vehicle in this condition should expect to put quite a bit of money into body work or mechanical repair, the carpet and other interior parts will have wear in excess of its age. This is a vehicle that has not been taken care of the way it should have been or has been used a lot more than it should have. It should however pass your local state safety inspection standard and be safe to operate on the road. A vehicle in this condition will usually not be for sale on a dealer's lot.
The second is Clean Retail. This means that the vehicle is in average condition. Everything should be clean, but worn the way that vehicle would expect to be given the age. Mileage will be reasonable and the paint will match completely. You shouldn't see panels that don't match. You shouldn't expect to put a lot into the vehicle to get it to 100 percent.
The third is High Retail. This is when the vehicle is in just about mint condition. You shouldn't have to put anything into the vehicle and it should come with someone sort inspection or warranty.
Consumers have to remember that these are just estimated values. A vehicle in mint condition might have an estimated value on NADA of $5725 but might actually be worth more. Fair market value is what a consumer is willing to pay, which often times is a lot more than the value that you get from NADA.
The NADA also has a dealer edition where the value on the same vehicle is much less. This is because a dealer is only willing to pay wholesaler for a vehicle. This edition also breaks the values down to include wholesale values, trade in values and much more.