The way it’s presented (x team reaches a certain level in xx% of simulations) you have a solid point. They necessarily have to add up to 100%. Even in factoring in rounding, it shouldn’t be off by 7%.

My guess is that it’s not in fact % of simulations, but instead % chance of reaching that level. Small difference in interpretation, doesn’t matter on the first round, but changes in the deeper rounds due to conditional probabilities. For example given Australia beats Argentina, their odds of reaching the semis is increased much more than say the USA beating the Netherlands.