The number next to a candidate or organization can be positive or negative. If you click on the score, two more numbers pop up. Those two numbers added together equal the displayed score.
Each of the numbers that make up a candidate score represent where you align positively and negatively with that candidate. Scores are summed from Stances, Political Parties and Endorsements.
If you and a candidate are aligned on political party, it's +2. Candidates of another political party do NOT get a negative score UNLESS you "oppose" = -1 or "strongly oppose" = -2 their political party as an organization.
In order for an endorsement to come into scoring, you must have an opinion of the organization (endorser).
Now we just sum all of that together to calculate a score for candidates or organizations that is PERSONAL to you based on your preferences.