Keep reading on the site, it will explain that to you.
This is listed on the page that gives you the price:
Value Explanation - N.A.D.A. has been collecting, analyzing, and publishing used values since 1933. The retail values listed are a guideline for appraisal purposes only. These values should be used strictly as a reference source for valuing used vessels. It is not, and should not be considered absolute. The values are a reflection of the boats condition and popularity. It may be necessary to adjust listed values to meet market conditions in your area. While on line values are similar to other N.A.D.A. published values, these values are intended for retail consumer use.
Low Retail Value - A low retail valued boat will show excessive wear and tear either cosmetically and/or mechanically. This boat will require cosmetic or mechanical work and may or may not be in running order. The buyer can expect to invest in cosmetic and/or mechanical work. Low retail vessels usually are not found on a dealer's lot.
Average Retail Value - An average retail valued boat should be in good condition with no visible damage or defects. This boat will show moderate wear and tear and will be in sound running condition. The buyer might need to invest in either minor cosmetic or mechanical work.
Note: Vessels in exceptional condition can be worth a significantly higher value than the Average Retail Price shown.