When supplied with a value for /LINES, /CALC will calculate the font size so that your output will fill the page less the top and bottom margins. /CALCULATE will only make the font size large (or small) enough to fit the number of lines you specified onto the page. It will not check to see whether the horizontal length of your lines will fit within the left and right margins. This command must be used with the /LINES qualifier and cannot be used with the /SIZE qualifier.