Making ball park offers on phone

[Jason Evans]

Im looking at a property thats a several hour drive from me so I wanted to to give the owner call and give a ball park offer to see if we are in the same range before driving there to take a look at the place. Ive already ran my numbers and only communicated through email.   Im wondering if it would be beneficial when giving my ball park offer to explain how and why I came up with the number or to just say the number.