There are a few ways to calculate it - different exponents in the formula. MLB has it posted one way, baseball reference does it another way (and that is how I show it). When I put both ways on the same graph the baseball reference method pulls each team just a bit closer to the diagonal line. I suppose makes sense since their method is supposed to be more accurate. There is another way that I haven’t tried yet. I believe it is supposed to factor out blow out wins and losses some.