Look under the 'mixed species heritage' advantage. They state that you chose the two parent races and 'mix and match' - You pick the 'best' stats from either and select skills from the main parent culture.
That's the mixed species advantage (+6).
By the book, when creating such a character, you choose wich of the races are dominant, then you take three Attributes from the dominant species' template, and the two others from the other species' template. You then choose the skills belonging to the dominant template (although IMHO that really depend of the background of the character).
The book says nothing regarding typical advantages/disadvantages, nor the fact that you could "breed" some rather stronger species that way.
Personnally, I would recommend to check whether the resulting mixed template is still based on 50 DP, optionnally counting the Mixed species advantage with the template. As for the skills, wich ones you get depends mainly of the background (you could mix both templates for the skills too, or lower some skills from one template).
Anyway - these are the formal rules and some observations of mine - take what you want.
Hope it helps
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