Well, when you use locally managed tablespace, the STORAGE clause is ignored. The extent size is either equal to the "granule" (in case if the tablespace is with uniform extent size) or is authomatically determined by Oracle (in case if extent pollicy is authomatic)
The storage clause however does not causes any error, for backward compatibility.
Only the initial extent and the min extents clauses are in force, meaning that at the segment creation are allocated as many extents, as specified in the min extents clause or to reach the initial extent size.
Generally, isnce you use locally managed tablespaces, I supose you use 9i or later and I would recommend using authomatic undo management feature