Your numbers are fine - but RNA is fragile; making one copy of something really rare will not be able to do anything as it will not last long enough to meaningfully contribute.

Interestingly we now are thinking about ways to use mutations in other ways, youve spent a lot of energy making these polymers, so it would be a shame to waste that right? We think that they can be used to assemble larger functional pieces as mutations are mostly deterministic meaning you'll get the same kinds of errors - so why not put them to use!