Well, it's very simple. The Evolution's name is "Claws" (plural), and the name of the Natural Attack in the table is "Claw" (singular). Does the Claws evolution give 2 attacks, each dealing 1d4 + STR / 2 damage, or does it only give one?
The Claws evolution grants 2 attacks
You can find the description for this evolution here (emphasis mine):
An eidolon has a pair of vicious claws at the end of its limbs, giving it two claw attacks. The claws deal 1d4 points of damage (1d6 if Large, 1d8 if Huge).
It is quite clear that the evolution grants two attacks from this description