I guess you need to say 2-5 odds
indeed this is not 40% because calculation is as follows:
you add 2+5=7 and then calculate 2/7 which is approximately 28.57%
the reason is that 2-5 means that winning 2 but loosing 5 out of total 7 possible outcomes.
Hope this explanation makes sense. Let me know if there are any questions and please do not hesitate to request me in the future just begin your post with "For David" and I'll revert immediately if I'm online