The "Season Stats" link for the player register stats set is to be used for best and fairest corrections - ie, it's a way to manually "fudge" the best and fairest stats for the season.  If for example someone is off ill for a month, or joins half way through the season and you want to give them a fair chance of winning the best and fairest award for the season, you can use the "Best and Fairest" correct to manually allocate a best and fairest value to them - an average of the best and fairest values of all the other players for example.  This correct will then be added to the sum of all the "Rating" values that the player has received for individual fixtures.