your talking about marine yes? I would say 0, i doubt you could fit all the necessary equipment in a 10g tank, im not an expert on marines but im sure damsels are recommended to have 30g each as they grow and can be aggressive.
Good to hear, as i said im no expert on marines, although i see you were told the same thing in the marine section that 3 damsels is already way to many to have in a 10g.