there are a few different ways to think about this...
you could consider this a ratio. the success rate here means that out of every 100 orders, 80 are handled within a day.
You can cross multiply and solve for X, or you can do something much simpler...
80/100 = .8
.8 * 240 = 192
you did something kind of interesting, though. instead of evaluating for 80% of the orders, you evaluated for 20%.
your answer:
20/100 = .2
.2 * 240 = 48
hope this helps.