Hi Ruud,
The lens that the camera uses is 6.3-63mm, that's the optical zoom. Anything past 63mm is using the digital zoom meaning the lens is not the one doing the work, it's the computer inside the camera.
I'm not sure how familiar you are with cameras, but optical zoom results in better quality than digital zoom, because the lens is acting as binoculars, really. Digital zoom is like falsely enlarging the image to make it appear larger, which is why this max zoom pic
here doesn't look good at all.
That aside, this is a 10x Optical lens (63/6.3 = 10). I guess in a sense, the 253mm max results in a 40x Digital zoom, but it's Optical that really matters. I may not be entirely accurate, but that's how I understand things.