It goes something like this... 1 person infects another person R=1. 1 person infects only 30% (un-jabbed) = 0.3 of a person or R= 0.3

Of course it the natural R number is 10 then 1 person infects (30% of 10 people) or 3 people.

So you have to guess that 30% = R1 so the actual R number is 100/30 or 3.3333

So if the natural R rate is 3.3333 and 30% are un-vaccinated you won't see an increase in the number of infected, they will just roll around getting infected, having the virus, passing it on, and then getting better.

That's if the vaccines work.