SAP Sybase IQ automatically reserves the minimum of 200MB and 50 percent of the size of the last dbspace.
To ensure that you have enough room to add new dbspaces if you run out of space in the future, set the database options MAIN_RESERVED_DBSPACE_MB and TEMP_RESERVED_DBSPACE_MB to values that are large enough to handle running out of space during a COMMIT or CHECKPOINT.