When exporting FBX files in general, you can export a maximum of 250,000 polygons per file. However, with the Unity game engine and Maya LT on the same system, you can export scenes directly to your Unity project with no polygon count restriction.
To export the scene to your Unity project
(You need to set the project only once. It's not necessary to set the project again for subsequent export operations.)
Maya LT exports the selected objects or the entire scene to your Unity project. If you have the project open in Unity, you can access the FBX file immediately. To see it in your Unity scene, drag and drop the file from the Assets folder in the Project Browser into the Scene view.