Target iOS Version quick question

Heya.

I want to publish my game for iOS 8 and above. The thing is that, the latest Unity 4.5 doesn't have iOS 8 in Target iOS Version.

I can set it in xCode, but my question is: If i set it to xCode to 8, what shoud be set in Unity Player Settings? 7.1 or Unknown, which one is better, or it doesn't matter.

Woud it be problem if i set it in xCode?

Why i want, is because i want to restrict my game to be available to only the newer iOS devices..

thanks