The number of fluid ounces in a pound depends on what liquid you are measuring. For instance, 16 fluid ounces of olive oil weighs 0.95 pounds. The same volume of water weighs 1.04 pounds.
A fluid ounce is a unit that measures volume. A pound is a unit that measures weight. Therefore, the question of how many fluid ounces are in a pound is meaningless until the measured liquid is known. The same volume of one liquid will weigh more than the same volume as another because it is more dense. In the example of water and oil, water is denser than oil. Therefore, 16 fluid ounces of water weighs 1.04 while 16 ounces of oil only weighs 0.95 pounds. The same volume of mercury weighs more than 14 pounds.