All you have to do is to set the format for the column to something like
<< Format( "Fixed Dec", 6, 0 );
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
d2 = dt << Summary(
	Group( :age ),
	Mean( :height ),
	Freq( "None" ),
	Weight( "None" ),
	Link to original data table( 0 )
);
Column( d2, 3 ) << Format( "Fixed Dec", 20, 0 );
d2 << New Column( "new", formula( As Column( 3 ) ) );
d2 << run formulas;
Column( "new" ) << deleteFormula << Format( "Fixed Dec", 6, 0 );

To capture the original format, and use it I found this method to work
Eval( Parse( "Column(d2,4) <<" || Char( column(dt,4) << get format ) || ";" ) );
 
					
				
			
			
				
	Jim