How can an animal regeneration produce two results?

Answer: Animals can regenerate in two ways: A complete organism or a part of the organism.
Explanation:
The regeneration can be defined as the process by which a part of the organism is produced or a whole new organism is produced.
The regeneration when takes place in the lower organism where whole whole organism is regenerated. Example: Planaria, hydra et cetera.
In case of higher organism where the whole organism is made of different types of cell, it is not possible to synthesize the whole organism.
In this case a small part of the organism regenerates. Such as the injury can be recovered in higher animals.