Question on "Sizing the PGA in Oracle 19c - How to Account for the MGA Size (Doc ID 2808761.1)"

a query is used to estimate sizing:

REM ===

col max_pga for 99999999.9

select value/1024/1024 max_pga from v$pgastat where name='maximum PGA allocated' MINUS    select value/1024/1024 max_pga from v$pgastat where name='MGA allocated (under PGA)';

REM ===

I doubt that this will bring the intended result as MINUS operates on tuples.

Please correct me if I'm wrong about the intended result:

REM ===

select

 max_pga/1024/1024 max_pga_mb, max_mga/1024/1024 max_mga_mb, (max_pga - max_mga)/1024/1024 diff_max_pga_mga_mb

from

 (select value max_pga from v$pgastat where name='maximum PGA allocated') a,