Looking at this really quick, I don't see where you are dealing with removing 75% of the sheep population in months that are multiples of 4. I do see you removing 1/2 the sheep population if over 10,000 sheep.
Is this the right challenge?
NOTE: Search the forums before you spend any points to get the Hints or Solution.
Read through this code, it seems like you are ignoring one specific condition.
Good Luck! Keep Coding.