The rate is 17% of your income if you only support 1 child. However if you have an additional child to support, the CM for the original child decreases to 14%; two additional children and it decreases to 13%; three additional children and it decreases to 12%.
So, say a man has a child with his ex, then remarries and has three children with his new partner - How come the first additional child reduces original maintenance by just 3%? And even worse, the next additional children only reduce it by 1%. Surely each new child has a bigger impact than that??