(R)eload for a new set of numbers.

The line number corresponds to font size in some arbitrary sense. Rendering quality may be impacted below 20, so consider viewing from further than arm distance, unless testing for presbyopia, in which case get as close as it helps to. Given all the factors involved there's no absolute standard for what line somebody with 20/20 vision should be able to read; instead this is more useful for testing if a new prescription is better than your old one, or comparing between people, etc.