Having It Vs. Understanding It

I'm scoring final exam projects at the moment, using a holistic rubric that aligns to my scoring system.  As I put in scores in my gradebook, students are contacting me via Edmodo with questions such as this:
"But I mentioned that in my project. I had it in there.  Why didn't I get a 10?"
Because simply having something about the concept isn't the same as demonstrating understanding of the concept.  
That's a tough distinction to make for students who have been raised in a right/wrong system of school for all their schooling years.  If they mention it, it must be right.  If I write more, I'll get more points.  For years I admittedly albeit unknowingly helped inculcate this attitude, with my rubrics where the only difference between some of my evaluative criteria was how many or how much students put down or how many mistakes students made - but nothing to do with the quality of the evidence they were providing.
When I score now, I look for quality, not quantity.  I look for how well the evidence students have provided to me demonstrates their understanding of the objectives in the rubric.  And then I rate how well their evidence shows understanding, on my 5-10 scale that unfortunately uses numbers that students confuse for points. (If I could get away with using symbols, I would, just to render scoring completely pointless, pardon my pun.)
Just because students mention a concept doesn't mean they understand it.  Score for understanding, not just having.