Your camera is most likely shooting in JPG mode. At 14MP, the GENERAL average would be around 1800 shots, assuming a 4MB file size per photo. However, when you take photos your file size can vary greatly, depending on what's in the photo. Color pixels take up more space -black pixels don't. So much depends on what's in your photo - take a photo in the dead of night, where you can barely make out one small streetlight, and most of the rest of the photo is black...then compare that file size to a daylight photo of a colorful quilt laid out on the lawn. The daylight photo of the color quilt will have a significantly larger file size, because pretty much every pixel in the photo is displaying a color. The more black pixels, the lower the photo's size. So while you might fit 1,400 bright daylight photos of very colorful detailed scenes, you might fit 3,000 nighttime photos with very low detail and lots of black. That's why those capacity ratings are just guidelines to give you a general idea.
Other factors such as what JPG compression mode the camera is set to will also affect the overall file size.
Hope that helps!