The article doesn't say this flare is releasing 10 percent of the Sun's total energy. Instead it says:

"A good flare can release up to 10% of the Sun’s total energy, the equivalent of billions of nuclear bombs exploding. What’s funny to me is that this wasn’t all that big a flare; it was rated as a class M2.5, far lower in energy than the vast explosions from the Sun back in February."