Heart Murmur

My dog (10yo 35lb Bichon) has a heart murmur that was discovered six months ago. They said the grade was 1-2. We just had his six month checkup to see how his murmur is and they said it got better and it's a 0-1 now. My assumption was that developing one at his age is different than when puppies have a murmur and it won't just get better. We don't always see the same person when we go to the vet so this person was different from the one who diagnosed him. is it possible that last time it wasn't actually as bad as they thought? or maybe it just didn't sound bad today? I guess the phrase "it got better" kind of confused me. Maybe I should call and ask. I was too thrown off in the moment because I worry so much and absolutely expected it to have gotten worse.