2576496 - "Main IQ Blocks Used" on sp_iqstatus - SAP IQ

What does "Main IQ Blocks Used" mean on sp_iqstatus?

For example, there are the following dbspaces:

======

DBSpaceName        DBSpaceType    ...     Usage    TotalSize     ...
--------------------------------------------------------------------------
 IQ_SYSTEM_MAIN   MAIN              ...        21         1.55T    ...
 IQ_SYSTEM_TEMP   TEMPORARY    ...          1          785G   ...
 iq_main                  MAIN              ...        95         4.6T     ...
 ...
==========

Iqmsg shows message run out of space:

==========
I. 10/30 07:15:19. 0000036578 Txn 1742033845 0 1742033845
I. 10/30 07:15:19. 0000036578 Cmt 1742033846
I. 10/30 07:15:19. 0000036578 PostCmt 0
I. 10/30 07:15:19. 0000035735 Exception Thrown from s_blockmap.cxx:4497, Err# 0, tid 2141 origtid 2141
I. 10/30 07:15:19. 0000035735 O/S Err#: 0, ErrID: 2096 (s_nodbspaceexception); SQLCode: -1009170, SQLState: 'QSB66', Severity: 14
I. 10/30 07:15:19. 0000035735 [20223]: You have run out of space in iq_main DBSpace.
-- (s_blockmap.cxx 4497)
=========

The procedure sp_iqstatus was reporting 78% of 'IQ Blcoks Used' :

      =========
      Main IQ Blocks Used: 646814875 of 826261725, 78%=4934Gb, Max Block#: 121937061
      ==========

• SAP IQ 15.X
• SAP IQ 16.X

sp_iqstatus,  "out of space" , iq_main, DBSpace , IQ_SYSTEM_MAIN, sp_iqdbspace, sp_iqfile, , KBA , BC-SYB-IQ , Sybase IQ , How To