By default admin will show the name of your model appended with an “s”, aka the plural form of your model. It looks like this
_images/plural.png
You have been asked to set the correct plural spellings: Categories and Heroes
You can do this by setting the verbose_name_plural in your models. Change that in your models.py.:
class Category(models.Model):
    ...

    class Meta:
        verbose_name_plural = "Categories"


class Hero(Entity):
    ...

    class Meta:
        verbose_name_plural = "Heroes"
With the changes your Admin will look like this.
_images/plural_fixed.png