Hidden Parameters default value

Hi,

I have run the below query to find the default value for the hidden parameters, but not understanding the meaning for  the   (b.ksppstdf  Default_T_F).   What it is indicating especially for the parameter :_smm_auto_min_io_size.  Basically I am wondering why that parameter default value showing as "TRUE" when current  and default values are different.

Could you please shed the light on it?.  Your help is very much appreciated. 

SELECT
ksppinm   name,
ksppstvl  Current_Value,
b.ksppstdfl Default_Value,
b.ksppstdf  Default_T_F
FROM
x$ksppi a,
x$ksppsv b
WHERE
a.indx=b.indx