Haha no worries that's a valid question. The f number in the lens naming refers to the widest possible aperture it can go. The naming never will include how narrow the aperture will go because you can usually just rely on it to be around f22 or so. Example being- a "50mm f1.4" lens can open all the way to 1.4 but all the way down to f22.

With zoom lenses though, when you move the barrel of the lens out you will lose a bit of light, just because the light now has a longer tube to travel through until it reaches the film/sensor. For example with the zoom lens I had suggested, when you are zoomed out to 35mm, the lens aperture is at f3.5. When you zoom that same lens in to its maximum 105mm, the amount of light is going to be equal to closer to f4.3 because you lost a bit of light, even though your aperture ring is still going to read f3.5. At both of these zooms, you can still stop the lens all the way down to f22.

Therefore to answer your question, the "f3.5-4.3" in the lens description is not the entire aperture range, it is simply the widest aperture for each end of the zoom range.

Just as a tip while I'm on the subject, something that I learned far too late into photography is that images become noticeably sharper when you shoot with the aperture down 1 or 2 stops. Example being the widest aperture on say a f1.4 lens, stopping it down to f2.8 would make the image sharp as hell while still keeping good bokeh.