That's certainly a point of contention. I tend to go by writing/meaning to count knowing one. But then that's more like half or two-thirds knowing the character, but it gets really tricky if you want to count all of the readings because who can really say they know 生? Alright, I'm sure there are those out there who can say it, and it is an extreme example, but the fact remains that there are lots of readings with different meanings for that character, and it really does take a while to really know it.