Unfortunately, I'd say that it's automatically useless due to the Calm nature, even if its Special Attack IV is flawless.
Do you soft-reset for your eggs? What you should do is, when the daycare man has an egg, save in front of him. Take the egg and hatch it. DO NOT take any more eggs from him. If the hatched egg is Modest but doesn't have Mischievous as its characteristic, soft-reset, take the egg again, and hatch it again. Since all but IVs are determined when the egg is produced (IVs are determined when you take the egg), once you get a Modest Yanma, you can soft-reset until you get good IVs.
If the hatched egg isn't Modest, then release it and save in front of the daycare man again, and repeat the whole process. The reason why you shouldn't take any more eggs after you take the first one is twofold: 1) you might not have another egg to take and soft-reset on if the first egg you got wasn't Modest, and 2) it has been proven that the more eggs you have in your party at once, the longer it takes to hatch all of them.
I hope that made sense, it's very complicated but this method of soft-resetting for IVs is a great way to get good IVs with the right nature quickly, rather than taking and hatching a whole bunch of eggs and hoping for the best.