Heart Murmur More Condition_symptoms. How Common/harmful Is A Type 2 Heart Murmur?

How common/harmful is a type 2 heart murmur? - heart murmur more condition_symptoms.

A friend of mine said a rescued Rottweiler age of 11 weeks, and the vet, he had a heart murmur Type-2. The vet did not think it would be harmful to the health of the dog, it will grow. What is the significance of heart murmurs? and nobody had a problem with a dog who has one?
In addition, Rottweilers are more likely than any other dog?