I presume that you mean the word count, as opposed to the size of the vocabulary.
What significance do you attach to the word count of a translation of the Scripture? And for that matter, what significance do you attach to the word count of a Greek critical edition?
Keep in mind that a number of counterfeit documents are bound into most English editions of the Bible, including the Geneva. These forgeries include the Book of Esther, the Book of James, the Book of Revelation, the Book of 2 Peter, and the Book of Jude. Also some English editions include a collection of non-canonical documents, which collection is termed "The Apocrypha".
It is likely that someone has made the count and has posted the count on the Web, particularly now that most translations have been published in machine-readable form; if so, you can find the count with a search engine.
P.S. The word count for the King James Version is roughly 750,000. The count for the Geneva should be roughly the same.