A player’s Round Score is calculated to show how they performed relative to the field on the day in question. For each individual day of a tournament, the mean and standard deviation are calculated, and Round Score is a player’s Z-score based on those preliminary calculations. Essentially, a Round Score of 1.00 means a player was exactly one standard deviation better than that day’s mean.
Season Score is the cumulative Round Scores for a player over a calendar year (which doesn’t always align with an official PGA season’s calendar), and Career Score is the cumulative Round Scores over a player’s entire career.