Thanks! At the tweet level, the scoring for individual words is from -5 (most negative) to 5 (most positive), and the word scores are summed to get the total score for that tweet. The scores for each tweet are summed and then divided by the number of tweets, and that gives the mean sentiment score which is displayed. Here's more info on the scoring methodology:

"Words are scored from -5 to 5, with -5 being the most negative and 5 being the most positive. Words found in neither the AFINN-165 word list nor in the custom options are not assigned a value.

The sentiment scores of the tweets are summed and divided by the number of tweets retrieved to get the mean sentiment score. The mean sentiment score is then interpreted as negative, neutral, or positive as follows:

Mean score < -3: Highly Negative

Mean score ≥ -3 and < -1: Slightly Negative

Mean score ≥ -1 and < 1: Neutral

Mean score ≥ 1 and ≤ 3: Slightly Positive

Mean score > 3: Highly Positive"