Hi @lala ,
I believe you can achieve that you're after with fewer steps in JSL. Below is a code that formats the new formula column with 2 decimal places. In the command Format("Fixed Dec", w, n), the first number "w" is the width of the field and the second number "n" is the number of digits after the decimal to keep. Not that I did not do the rounding in this example for the formula.
In your JSL, you are setting both the width and number of digits after the decimal to 20, so this is why you get the output you see.
Names Default to Here (1);
dt = Open("$Sample_data/Big Class.jmp");
New Column("A", Formula(:height/:weight));
dt:A<<Format("Fixed Dec", 6, 2);
Hope this helps!,
DS