Game analysis scores?

How do we know much of an advantage one side has when the computer gives scores based on position? I think that 0 is totally drawish, 0.1 is a very minor insignificant plus, 3 is a good plus, 7 is a moderate advantage, and 93.05 is a queen up in the endgame against a bunch of scattered pawns and nothing else but a doomed king.

I believe up by 1 point means that the possition is such that you are up something about equal to a pawn be it an actual pawn in an otherwise equal possition or a possition where you are possitionally better enough that you'd have been willing to sac a pawn to get there. (It could also mean you are up a piece but your opponent has some possitional compensation) 

give you a tip about assessments by computers for the most part just ignore the constant value and look at what the trend is over 5 moves is it the same? going up? going down? thats what tells you a lot more about things than some static value other than a forced mate or draw. Dont even trust 0.0