RangeMin and RangeMax of points coordinates


I have to create a “.vtp” file (xml file for polydata object) from a model of simulation. I have found some examples on the internet to understand the construction of this kind of file. However, I don’t understand “RangeMin” and “RangeMax” of the . It seems that they are not minimal and maximal values of coordinates of points ? Can you tell me what they are - the values of “RangeMin” and “RangeMax” of the ?
Thank you very much.