This is it. It is the handlebar stack and reach that you are shooting for. I call it the finished bike stack and reach. If you know what stem and spacers the fitter was using to convert the frame stack and reach to the required finished bike bar stack and reach, then you just adjust those to accommodate differences you may encounter in the frame that you are looking at. Because of the angles, the changes aren't so simple, but you use an online calculator to help you adjust for the frame differences. Here is a popular one: Stem Comparison Tool | yojimg.net