When you think in terms of ounces and pounds, measuring can become quite tricky. But when it comes to flour, it is a bit easier. Just remember 1 pound will always be 16 oz. 16 oz will almost always be 2 cups.
There are odd cases in which denser flours yield a tablespoon less, and some where lightweight flours yield a tablespoon more.
This happens so infrequently that measuring your flour should fix any problems.