Your question is not clear as stated. If you want to know the limit, use LISTCAT ENT(gdg.name) GDG ALL and look at the HISTORY section of the output:
HISTORY
DATASET-OWNER-----(NULL) CREATION--------2009.288
RELEASE----------------2 LAST ALTER------2012.252
ATTRIBUTES
LIMIT-----------------32 SCRATCH NOEMPTY
If you want to know the currently defined generations, look at the ASSOCIATIONS section of the same output.