I have spoken to a few peers across the industry recently and I have noticed a few planners and forecasters have fallen into a little trap.
Always make sure that the stakeholders outline the actual inbound service levels, including methodology. I have inserted a few examples to show how inbound service level measurement can differ dependent on needs/wants.
If you presume a service level that is different in methodology to what is actually outlined, you can find yourself reporting on markedly different figures, leading to all sorts of problems!
Conclusion - Check!