Massive deviation of tablespace max_size compared to bytes used by segments on that tablespace
The way you have acquired the tablespace size is incorrect.


  MAX_SIZE(NUMBER) returns Default maximum size of segments (in Oracle blocks).


You can query dba_data_files and dba_free_space to get the result

Following is the exceprt of monitoring script that we have been using.

SELECT * FROM (SELECT a.tablespace_name, SUM(a.tots)/1024/1024-SUM(a.sumb)/1024/1024 Tot_Used_MB, SUM(a.tots)/1024/1024 Tot_Size_MB,   
SUM(a.sumb)/1024/1024 Tot_Free_MB 
FROM (SELECT tablespace_name,0 tots,SUM(bytes) sumb
FROM dba_free_space a  GROUP BY tablespace_name
UNION  SELECT tablespace_name,SUM(bytes) tots,0 FROM  
dba_data_files GROUP BY tablespace_name) a GROUP BY a.tablespace_name);