How do you interpret the idea of balancing the Force? It’s a more subjective answer than you might expect. George Lucas defines balance as the removal of the toxicity of the dark side, a la the removal of toxins from blood. You return things to balance by eliminating whatever is causing them to go out of whack; thus, you keep the Force in balance by making the light side pure and free of the dark side. That’s what the Jedi seem to think as well; in the original trilogy, they want Luke to take out Darth Vader… which, really, is not very Jedi-like.
Balance could also mean leveling the playing field so that there’s an equal amount of Force users drawing from either side of the well. Boiling it down to a numbers game seems like an oversimplification, but it’s a possibility.