Smileless I don't have the actual figures, but it works like this:
Let's say that on Day 0, there are 100 cases. Left unchecked, the number of infected people doubles every three days, so by Day 3 there are 200 cases.
By Day 6, there are 400 cases; Day 9 800 cases; Day 12 1600 cases; Day 15 3200 cases and so on.
The above is what was happening in the days before lockdown and until the effects worked through the system.
If R=1 (ie one person infects just one other person) there will be 100 cases on Day 0 and 100 cases on Day 15.
However, if the rate of transmission can be reduced, so hardly anybody infects anybody else, the numbers start to look very different, eg
Day 0 100 cases; Day 3 50 cases; Day 6 25 cases; Day 9 12 cases; Day 12 6 cases; Day 15 3 cases.
That can all be worked out mathematically. I don't have the exact data, but the scientists at Imperial College do and can work it out much more accurately.
In my example, it's easy to see that "locking down" makes a huge difference.
Once the number of infected people is manageable, It's possible to deal with them. If necessary, you could put them up in a luxury hotel for a couple of weeks, make sure they have everything they need, compensate them for loss of earnings, etc. They just need to be completely isolated. The virus would disappear because it has no host. It can't continue in the atmosphere for long.
Effectively, that's what New Zealand did and is now reaping the benefit. The UK dithered for too long until the numbers started getting out of control, which is why it's now so painful to return to anything like normal and there will be long term consequences.
Scientists (and others) are worried that we still haven't got the numbers low enough to risk a rise in infection rates. The UK is dithering again. It really does seem that decisions are being made for political reasons and to please voters rather than having a coherent plan to virtually eradicate infection. We have short term gain for long term pain, where it should be the other way round.