The idea behind tree balancing is balancing of goals' and categories' weights.
The weight allows to specify the relative importance of the goal or category.
Another rule is that the sum of all weights on the same level and within the same category must be 10. Sure, it might be 100 or 10000 or 5, but it was found out that if the weights are specified on 0..10 scale, they are getting the best results in representing relative importance of the items.
If you click on any category or goal you will see a setting panel below. You can change the weight from 1 to 10.
What if you have tree goals - A (weight 2), B (weight 5), C (weight 7) within the same category. The sum of the weights is most than 10.
If the sum of the weights is more than 10 (as well as if it is less than 10), you should change the weights to comply with the weights sum rule. You have two options to do this:
Actually, you have the third option, you can leave weights "as-is" but in this case the total performance value might be more than 100%.