Well, I translated what you said into Chinese in my mind and get what those Chinese really said. In Chinese, we often use 70% and 30% as a way to indicate both sides exist but the 70% part comes with more weight. It's not to say that is exactly 70%. Their original words are probably like this: 毛主席七分功，三分过。 Just to make this expression more clearer.
First time to hear that. If you are Chinese grown up in PRC as well, it's most likely you are younger than I am. Also, what I said is not some content directly from a specific source. Even there is some kind of "standard" from the authority in some way, the possibility that people have exactly same consensus in this regard.