Student already covered it, but here is the expanded version.
If you go to this website:
http://www.usatoday.com/sports/sagarin/fbt11.htm
You will see that there are several columns. If you go to the far right, you will see two columns of numbers. The blue numbers are labeled PREDICTOR and the red column is labeled ELO_CHESS. The blue column includes all factors like W/L record, strength of schedule and score margin. When the BCS approached Sagarin to include his numbers in their computer rankings, they forbid him from using some factors in his calculation, including margin of victory. All that was allowed was W/L record and SOS. Those results make up the red column. When USA Today started running Sagarin's results, they wanted something that included both figures. So Sagarin created a third set of results that basically averages the two numbers(not exactly, but close). This third set of numbers is labeled RATING and is colored purple.
So which to use? Sagarin makes this comment in his introduction at the top of the webpage linked above: (emphases mine)
Since Sagarin says PREDICTOR is the most accurate, that's the one I go with. The conference rankings are also recalculated using the PREDICTOR numbers and the central mean method.
I normally have to re-explain this about every third week.