So, a couple examples of how to use those stats(or at least, of how I use them). I'm using myself, because I'm narcissistic like that(and because I know where the numbers came from). Some of what I say may be wrong, because this is largely stuff I've worked out on my own.
My win rate if copper is available is 1.28. That means that I tend to get 1.28 win points per game, and because I play almost exclusively 2-player, means I win an average of 1.28/2.00=64% of my games. Note that this has absolutely nothing to do with player skill, so the fact that it's higher than, say, chwhite's or WanderingWinder's winrates(both of whom are better than me) probably comes from a combination of me playing about 10% of my games against an IRL friend who I'm better than and playing automatch +/-20 for a long time instead of the +/-15 or +/-10 that I think both of them use.
My winrate with outpost is 1.71 and my Effect With is 3.86. Does that mean I have some insane insight into the card? Well, not really; if we look at %+, I only gain it in 18.5% of games where it's available, because I use it mostly as a win more type of card, to turn a 90% win into a 95% win when you're using minions or something, which means I get almost exclusively in games I would've won anyway.
Speaking of minion, my effect with minion is -2.10. Is it because of bad luck or something? Well, no; there's something I don't get about how to play the card, and the only reason my winrate is still >50% with it is people occasionally do silly stuff(
This game probably being the best example of that, there is no way I should have won that game).
My effect without hamlet is 2.66, but my effect with is -0.56. However, I also get Hamlet in 91% of games, so what that means is that when I think my deck doesn't want hamlet, I'm usually right, but I'm not very good in games where I should be buying them(which I believe is most games).
My effect with Ambassador -0.76. That's because I've bought it a lot, but the winrate is still below what councilroom expects(which I think is my overall winrate times the winrate the population as a whole has with ambassador, so 1.28*1.04=1.33).
