Hi!
In this case Moz, isn't the smartest with their tool. What they're doing here is just checking the total source code apparently for the number of keyword matches in there. But what this does is that it's also checking all your META tags in the head. In your case I see at least another 4 mentions in there from OG:Description, OG:Title and Twitter:Title and Twitter:Description.
Another 4 mentions are currently happening in your Schema.org at the top for Organization, that's where I just stopped looking for more instances as they're probably just hidden somewhere else in either ALT tags or other snippets.
So I would, in this case, go with your own calculations for just using the number of mentions that is on the page and ignore the number that Moz is reporting here. Hopefully, Moz will change this over time and only check the occurrences in the actual BODY content.
Martijn.