The numbers on a Stübben saddle refer to the size and model of that particular saddle. The first two digits represent the tree width, followed by an X or R, which stands for either extra narrow or regular respectively. After that is a three-digit code, which identifies the specific model of Stübben saddle. For example, if you have a 30X200000 saddle it means it has an extra narrow tree width (30) with the 200000 being its unique identifier as part of their product line up. It's important to note that these codes are not universal across all brands so make sure you consult your local saddlery for more information about what each number represents in relation to other brands.