I'll clarify a bit, just for you. The process isn't hard. Imagine for a moment you know how many ABs a player has, and their batting average... but you want to know how many hits they had. You simply multiply them together and voila! Well, we're doing the same thing... multiplying the expected batting average on balls in play (which is LD% + .120) by the number of balls in play. That gives you the expected number of hits in that situation. So now you have the right number of hits... you just have to figure out how to add the missing ones back in to the players actual line. Since all I'm trying to do in this situation is neutralize luck (and not bring their career lines into the equation at all), I simply add the hits back in the same ratio of singles, doubles, and triples they already had this season. There are two routes to go from here. Obviously, these numbers are going to be bringing back fractions... so you could either round them off and give the whole line, or just calculate AVG, OBP, and SLUG as is. Since these expected lines are supposed to read as a probability, it's more accurate to just straight out calculate the slash stats.