Okay, after a bunch of attempts, I think the SID is wrong. But this is probably my fault. The Pokemon Stats I gave you were from a hatched pokemon that was given to me in game, so that may have affected it. I was still getting the Nature is was saying I would, so I don't think I did it wrong. Here's another pokemon. See if you get the same results:
Pokemon: Unown
Nature: Timid, Likes to Fight
Level: 23
HP = 57, Atk = 39, Defense = 31, Sp. Atk = 41, Sp. Def = 28, Speed = 30
IDNo. 51098
Thanks for the help.