Math isn't my strong suit AT ALL, so I don't know the formula to come up with the maximum number of possible combinations, but 6 x 650 = 3900, which is a LOT of possibilities.
Your math it's wrong, with species clause the number of possible combination its 649*648*647*646*645*644 = 73 013 317 740 000 000; and without species clause its (649)^6 = 74 725 388 360 000 000
=)