Given the following enum:

enum Animals {
  CAT,
  DOG,
  PARROT,
  SHEEP,
  SALMON
}

The following mapped type:

type AnimalsToMappedType = {
  [K in (keyof typeof Animals) as typeof Animals[K]]: K
}

Results in:

type AnimalsToMappedType = {
    0: "CAT";
    1: "DOG";
    2: "PARROT";
    3: "SHEEP";
    4: "SALMON";
}

QUESTION

Given that:

typeof Animals['DOG'] === 'number`

Why does [K in (keyof typeof Animals) as typeof Animals[K]] result in the actual numerical index, rather than just number?