It’s only us, Burnley and Leeds left in the mix, and Leeds only have one game remaining (three possible outcomes). Each of us and Burnley have six possible outcomes. You can’t factor in actual score lines (e.g. 1-0, 2-1 etc) otherwise the permutations are limitless. So, you’d need to simply work on the basis of Everton/Leeds/Burnley have better GD/better GF/better GA/head to head records.
I dunno, maybe it does stack up to 243. Perhaps a stats whizz on here could validate?! If only to bring me some extra comfort that our chances of dropping really are in the 6%-7% range!