I could argue the number of breasts because I seem to recall that mammals give birth to no more offspring than they're able to feed.
The AM says that Aslan very rarely have twin births, so why four?
That's how they are drawn. Note also - many species have occasional multiple births with extra mammaries. Humans, for example - two breasts are the normative for Humans, and single birth is normative - typical nursing is alternating sides for each feeding.
Likewise, Goats have two, but litters of 3 are not unheard of.
Most canines have 8 nipples - but typical litter size is 5...
It's not as firm a rule as one might think. Perhaps the proto-aslan tended to nurse two chronologically separate births, much as Kangaroos tend to. (