chromosone 3

my son has chromosone duplication,shortarm chromosone 3, Ive googled this and can find nothing on it,
I understand about how meny pairs we have etc. when I was first told that my son had a extra chromosone,i googled and found info on chromosone 8, which I read and was convinced I would be told that my son would have chromosone 8.So im abit lost now I have been told its chromosone 3. Is there any information anywhere.
I am now waiting to see a clinical geneticist,but would love to be able to read up while im waiting.