value of a win

how is the value of a win decided 

in the same game, 1 win can be worth more than three wins 

First off, the rating change formula is different for every game, depending on the average rating of players in the game.

Assuming average rating = "a" for simplicity:

If a = 1500, the rating changes formula is 

1st = 3 wins

2nd = 1 win

3rd = 1 loss

4 = 3 losses

If a = 2400, the formula is:

1st = 3 wins

2nd, 3rd, 4th = all 1 loss

As you play higher rated games, you will see that 2nd place will gradually win less and that 4th will gradually lose less, transitioning into full solo (2400+) where all players lose the same.

Secondly, a lower rated player (or a player with a higher glicko rd (rating deviation, or accuracy of rating, higher being more inaccurate)) will sometimes be able to gain more than 1st place as a 2nd place finisher, if the difference in numbers is dramatic enough (see example below):

https://www.chess.com/variants/4-player-chess/game/28463805/119/4

the question is why  in the same game   3 wins is worth .03 or 1 win worth .03 /3=.01

but  .66 wins is worth 11.4  or 1 win is 17.5 

I already answered your question, but I’ll rephrase it.

I am almost 1500 points higher than @NITRO-NINJA, so they gain more because of the rating that they have. If they instead got first I got second, they would probably gain upwards to 80 points and I would get 0.1 or even less. 

i understaned that the number of point will vary 

I want to know how the value of win in a game is calculated  or do you make it up as you go along 

is there a way to know the value of a win at the start of the game 

you say 2nd place is going to be .66 wins so what is a win worth