fill field's value of model which is depend on another model

I have models

class Product(models.Model):
    category = models.ForeignKey(Category, on_delete=models.CASCADE, )
    name = models.CharField(max_length=50')
    seats = models.PositiveIntegerField()
    quantity = models.PositiveIntegerField(validators=[MinValueValidator(1)])

class ReserveModel(models.Model):
    products = models.ManyToManyField(Product, related_name='rented')
    rent_from = models.DateField()
    rent_to = models.DateField()

when I create instance of ReservetModel I have to have ability to point quantity of each selected product, how can I implement this?

Are you saying you want to track / find out how many ReserveModel are associated with a particular Product?

If so, what you don’t want to do is try and track it manually. Use the count function to get the number when you need it.

No, I mean, I wanna be able to point “quanitity” field of model Poduct when I am creating a ReserveModel instance

I’m sorry, I’m going to need you to be more verbose and explain exactly what you mean by “point “quanitity” field of model Poduct”. What do you want the quantity field to contain?