That really depends on what you're selling. If you sell air
conditioners, your sales
probably peak in July and August, but if your main product is
Christmas decorations,
then November is probably your biggest month.
If your line is something non-seasonal, like toothpaste or
toilet paper, and your sales
are exactly the same every month, then that's (8 and 1/3rd)
percent of annual sales
every month.