why domain ranks are not correct..

GSA shows domain rank like 5, 4, 3 etc..but in actual many times wrong.. why is this so.

that date comes from google. Nothing I can do really.

Maybe SER is getting the _page rank_ from the page instead of the root domain which you're checking, or the other way around? Wouldn't really know myself as I'm not checking pr, but have you made sure that this is not what's happening?