Well, I think that chart is a lot closer to reality than the one from the notorious "penis size debate" site.
My sexual experience hasn't been vast, but I've had about 14 or so female partners (only my wife for the last 27 yrs). My input is from that experience, and what I have been told, have read, or have overheard from women discussing penis size.
I assume that the chart applies to women's preferences for the purpose of vaginal intercourse. Most women seem to prefer something a bit smaller for oral or anal sex.
The overall most common "perfect" length that I have heard from women time after time is 7 inches. I have heard some women, who profess to be "smaller", to prefer 6 or even 5 inches. I have never heard a woman in real life to express a preference for 8 inches or larger. Obviously, I've heard women express a preference for this size on the internet, and I don't doubt that such women exist, but I don't seem to have encountered any, at least as far as I am aware.
As for girth, I think that very much depends on the woman. I suspect ideal for most would be larger up to the point that they started to experience significant discomfort either during or after sex.
I am about 7.6" BPenis EnlargementL (with an "insertable" length of a little over 7") and an average girth of about 5.5" with a maximal girth at the base of 6" or a little less, which would put me pretty squarely in the center of the red area of the above chart. I have not been too large to have vaginal sex with any woman I attempted it with. I have been considered a little too large by a couple of women, and several others told me they were glad I wasn't any bigger. Nobody told me they wished I had been larger, but then I expect they wouldn't have even if that were the case. And I did get the "it's perfect" response from a few, but then I suspect guys of all sizes hear that.
As for my wife, I used to make contact with her cervix years ago, and that was pretty uncomfortable for her, but usually only in certain positions. She never had any problems accommodating me girth wise. After 2 children and 2 vaginal deliveries, however, I no longer "touched bottom". Frankly, judging by the ease with which she can receive me now, I suspect I could be at least a half inch longer and perhaps even an inch bigger girth-wise before we encountered difficulty. Would it make sex better for her: I don't know. Would it be better for me: probably.
but this was not the point.
(if shes not running away of your killercock before you can ask her^^)