As discussed in To add a mode to a project, when you add a new mode to a project, you have the option to base that mode on an existing POF file, specified through the Add New Project Mode interface. This is one of two ways to make use of an existing POF.
When you are working in the Project Settings interface, you can click Reference to replace settings used in the current mode with settings from a POF. Although this changes the compiler, runtime, environment, and library settings for the mode that you have selected, the name of the mode stays the same.