4V7 is just another way of saying 4.7v, usually thats what appears on the zener anyway, decimal points tend to get lost on the component, which can be tricky. It also helps confirm that its a zener diode under consideration.
The wiring of the slider resistor is purely arbitrary - its just there to make sure that the capacitor does take some time to charge. The results would probably be the same if the connection between the top of the pot and the +ve line. The pot is what adjusts the timing of the charge, Q1 is an emitter follower observing the voltage and presenting it to the zener diode at a lower impedance, so Q1 does need to look at the capacitor voltage. The pot should give a good range of times, changing the capacitor would give a further range, as would using a different voltage zener.
There are lots of ways of skinning this particular cat, and its quite possible that the result could be achieved with yet fewer components, (741, pot on one input, R on the other, transistor output springs to mind) but unless I accidentally have a large cheese butty and a flagon of something potent for supper one night, probably not me.