The balancing algorithm tries to avoid changes of the corresponding Variable
If you move the slider more towards "Category" the algorithm will avoid moving slices from one category to another, but is more likely to change the number of slices you ordered.
If you move it more towards "Total Count" the algorithm will avoid changing the number of slices you ordered, but is more likely to move them from one category to another.
E.g. If you want to only get pieces from your chosen category put the slider all the way to the left