check @ Most allocated extents in any segment\
Refer note: 483856 - Description of the alerts for Oracle database monitoring
.2.3. Segments approaching max_extents---------------------------------------This is the number of segments that trigger red or yellow alerts for the "Fewest extents left before max_extents" node.Important: This alert has only an informative role for locally managed tablespaces (LMTS), where the max extents attribute is set to UNLIMITED and the next extents size is determined automatically by Oracle. As a result, the number of extents is no longer a critical factor for LMTS.