Well pg is talking about weekly growth, not monthly:

"A good growth rate during YC is 5-7% a week. If you can hit 10% a week you're doing exceptionally well. If you can only manage 1%, it's a sign you haven't yet figured out what you're doing."

Oop, yep, thanks!

Founders should aim for 15%+ monthly growth in MRR if they want to raise a Series A within a reasonable time after raising seed capital.