Initial Levels and Grids helps you to define the levels and grids that will be used in the project. For grids, allows you to create the orthogonal grid frame defining a different X and Y distance. For levels, it keeps the elevation of the first level in the project, allows you to choose a total number of levels and a standard space between them. You can choose to create the plan and ceiling views along with the levels. Grids can only be created in plan and 3D views, Levels can be created in sections, elevations or 3D views. You can choose to create only grids, only levels, or both at the same time (only on 3D).
This application is designed to be used in new projects, if the file already have several levels the application will give you an alert about posible information loss and element disasociation. There is no problem with creating grids in files with previous grid information, the application will skip the existent grid names.