There is 6 regular packs and 6 value packs so add those (6+6=12). Divide 12 by 2 (because there's 2 socks in a pair) and get 6. Then divide 402 by 6 and get 67 pairs. Do the same for the second location.
If you add 468 (amount of animals already there) and add how ever many more coming (192) then you'll get 680. If you add 100 more that will only be 780 animals.