At the Regaine home page they say that it oesn't help if applied to totally bald areas, what does totally bald area mean exactly?

does the hair that lost in the last one year for example has the possibility to regrow, or it can only help the newly lost hair.

My frontal hairline has been receding slowly for more than 5 years, but there is still some hair, it is not totally gone. So to what extent in terms of time passed for lost hair, could Regaine help these hair.