Width Field:
Samples (Width is in red): %1<%12.3f(E1-10)>
%1<%0.3f(E1-10)>
Width is the second optional field. This is a positive integer that determines the minimum number of characters to be output. If the number returned by the program is longer than the value you specify, then the entire results is returned. If then number is smaller than the width value, then the output is automatically space padded or padded with the character you specify. If you don't want any padding you can use 0.
The type specified also relates to the minimum width. For example, floating point numbers default to 6 places after the decimal. The precision spec is used to refine the number of decimal places to output.
See Width Field for more information.