True if the file is owned by user uname (belongs to group gname). A numeric ID is allowed.
True if the file’s numeric user ID (group ID) is n. These tests support ranges (‘+n’ and ‘-n’), unlike ‘-user’ and ‘-group’.
True if no user corresponds to the file’s numeric user ID (no group
corresponds to the numeric group ID). These cases usually mean that
the files belonged to users who have since been removed from the
system. You probably should change the ownership of such files to an
existing user or group, using the