(a)

The probability of hitting one of the players outs with the next community card is around 2% * number of outs + 2%.

(b)

The combined probability of hitting one of the players outs from the flop either with the turn- or river card is around 4% * number of outs (-1% with 9-12 outs and -4% with more than 12 outs).

I was wondering if someone could give me an example of both (a) and (b) respectively, especially (b) with the bracketed area on the end of the equation eg. what about less than 9 outs like 8? or 7? etc.....