Google-analytics – Google Analytics email when X happens

Perhaps you could play around with other options such as _setAllowAnchor() and change your URLs to use hashes (for GA) and query vars for your web app. Although, to be honest, probably not the best idea in the world to throw errors if you have unknown variables query strings, it should just ignore them instead.

Google defines unique visitors as "number of unduplicated (counted only once) visitors to your website over the course of a specified time period" http://support.google.com/googleanalytics/bin/answer.py?hl=en&answer=33087 so what is happening here is when you are looking at each day those numbers are correct for that day. When you expand the date range the numbers are different because you have 82 visitors (2334-2252=82) that came to the site on both days so they are counted as unique when you are looking at a single day but not when you are looking at two days.