Ranking is almsot completely relative. If one gets rank within a very well run organization, it might give one a sense of where one stands relative to other folks in the organization. Usually it really just gives one a sense of where one stands relative to the other students within the dojo.
Really, what it says is about how your teacher feels about your training and your support for him or her and the dojo. It is hugely subjective. If one understands that fact, one can keep from taking it too seriously. It's nice to move up the ranks, and certainly, itis nice to get a black belt as that is the moment when a teacher really puts his or her name on you. Most teachers do not wish to have a yudansha that doesn't "represent" well. So getting yudansha rank usually means the teacher feels you are representative of some standard that he or she has in mind for that level as they don't wish to be embarrassed or have the school's reputation damaged. If you are happy with your teacher, that should be enough. If for some reason you are dissatisfied, then a broader awareness of what the quality range is for a certian rank like Shodan might be meaningful to you, but maybe not.