Factors that can influence the number of puppies include:
* Age and health of the mother dog: Younger, healthier mothers tend to have larger litters.
* Breed size: Larger breeds generally have larger litters.
* Previous litters: Dogs who have had larger litters in the past may have larger litters again.
* Nutrition and overall health: Proper nutrition and good health can contribute to larger litters.
It's important to note: The number of puppies a Rat Terrier can have is just an estimate. Every dog is different, and there's no way to predict the exact litter size.