Hrrm. The math isn't working for me.
2Of every clean beast thou shalt take to thee by sevens, the male and his female: and of beasts that are not clean by two, the male and his female.
I follow that the language is clear that there are seven sets of male and female. However, the format of the later part of the sentence seems to be the same form as the first part; so instead of a single pair of unclean animals the language instead reads a set of pairs.
Sets:
7 sets (male and female) of clean = 14 each.
2 sets (male and female) of unclean = 4 each.
So is the translation quoted above incorrect?