What are the rules for the "fresh" (?) score on Splatoon2

There's a score on Splatoon2 which only appears before you play Turf Wars,

The rules seem to be roughly:

• If you win a lot of games, it goes up slowly

• If you lose games, it goes down very quickly

For example, I won 10-15 games of Turf and it got up to about 20. However I then lost one game, and it decreased all the way to 12.

• I think (but I'm not certain) your individual play seems to affect it as well as win/loss. (I don't know what affects it - kills? coverage?)

• I think (but I'm not certain) if you have a DC on your team it does not go down when you lose (same as in Ranked)

Finally I do not know the proper name of this score.

Does anyone know the actual rules of this score?

So this is called "Freshness", it's your rank for your main weapon.

Your Freshness rank increases by 1 when you win a match but decreases by a specific amount depending on your rank. Below is a table with the score you need to get to the next rank as well as the penalty for when you lose (apologies if the table is messy, Stackexchange has no option for tables)

Rank          Score   Penalty
Dry              0      -0.5
Raw              5      -1
Fresh           10      -1.5
SUPERFRESH!     15      -2
SUPERFRESH!     20      -2.5
SUPERFRESH!     50      -3  

The rating only increases/decreases based on win/loss, there's no other factors that come into play. If you have less teammates on your side compared to the enemy, you won't lose any Freshness rating.