Board Thread:Questions and Answers/@comment-3121860-20160504015940/@comment-24770490-20160507173825

You are wrong, you heard it in a fanfic and thought was true. 10 is just a random number which, aside from the show's name, has nothing to do with the DNA ratio.

They stated many times how the Omnitrix worked. It turns the user into a selected alien whose DNA sample is stored within the watch (or in a planet that has been retconned many times).