As to how many infections there are/will be in a population with an infection with an R of X depends on 1/ how many cases you start with 2/ the cycle time and 3/ how many cycles you have before taking measures to change R. There are formulas for this - epidemiologists will know this - are they wrong? I know some have come up with somewhat different results for R, but of course R is not fixed (unless you define it as such), and varies with both both time and place.

The biggest unknown - and an obvious influencer - is the cycle time - how long from being infected before someone then starts to infect others. If this is just a day, numbers will rise very quickly, if it is 2 weeks, it will clearly take much longer. Again, epidemiologists will know this, and have ways of estimating cycle time from the data available.

Do you feel R was a lot lower, and lockdown has had little influence, or that R was high, and far more have been infected than than the generally accepted 5% (10% in London)?