[Answer]-Django – How to increase the number of choices in a (multiple) select field?

choices for model field cannot be a callable, rather it should be tuple/list. Overriding it through __init__() method as is generally done for forms is not recommended for models.

You may want to re-design your models. You can create another model for choices that you have and have ForeignKey() relationship with Other model.

What you might have seeing about number of choices is the number of choices that are present when that model class is initialized.