@shrubbery: Please see attached image. If your contact has additional details, there'll be a white frame surrounding the avatar, clicking on it will bring up the additional details. Likewise, if the contact only has one number, there'll be no white frame around the avatar/blue image, and clicking it will do nothing.

edit: hmm.. how did you add a space in between numbers in the first place? I tried to do that but I wasn't allowed to enter a space on both keyboards

@Palleman: Unfortunately, at the moment, the OS only allows us to merge/add numbers that is not already in "contacts" if you do it under "call log", "Contacts" would be a better place if you want to edit or merge existing contacts