Default storage space - DB engine tuning advisor

Received this error when running the DB engine tuning Advisor (DTA)

The minimum storage space required for the selected physical design
structures exceeds the default storage space selected by Database
Engine Tuning Advisor. Either keep fewer physical design structures,
or increase the default storage space to be larger than at least 2
MB.Use one of the following methods to increase storage space: (1) If
you are using the graphical user interface, enter the required value
for Define max. space for recommendations (MB) in the Advanced Options
of the Tuning Options tabbed page; (2) If you are using dta.exe,
specify the maximum space value for the -B argument; (3) If you are
using an XML input file, specify the maximum space value for the
element under

The disk space used by the db < 8 M and the free space on the disk is
over 120 G.

Thanks,

jb