0 ) Digit placeholder. Display a digit or a zero. If the expression has a digit in the 
position where the  0  appears in the format string, display it; otherwise, display a 
zero in that position. 

If the number has fewer digits than there are zeros (on either side of the decimal) 
in the format expression, display leading or trailing zeros. If the number has more 
digits to the right of the decimal separator than there are zeros to the right of the 
decimal separator in the format expression, round the number to as many decimal 
places as there are zeros. If the number has more digits to the left of the decimal 
separator than there are zeros to the left of the decimal separator in the format 
expression, display the extra digits without modification.
 
(#) Digit placeholder. Display a digit or nothing. If the expression has a digit in the 
position where the # appears in the format string, display it; otherwise, display 
nothing in that position. 

This symbol works like the  0  digit placeholder, except that leading and trailing 
zeros aren't displayed if the number has the same or fewer digits than there are # 
characters on either side of the decimal separator in the format expression.