Below is the answer to your question:
Q: Why were there pending cases listed with priority dates after August 2007 when the Visa Bulletin priority dates was never beyond August 2007?
A: We have reviewed the source data for the inventory and have determined that a number of errors contributed to the appearance of cases with a 2008 or 2009 priority date in countries and preferences for which the priority date has not advanced beyond 2007 in the DOS Visa Bulletin. First, several of these cases had more than one approved I-140, and, rather than list the case by the earlier priority date, we erroneously listed the case by the later priority date. Several more cases were cross-chargeable to a non-retrogressed country but were listed under the retrogressed country. Finally, a handful of cases involved simple data-entry errors.
Source:
http://www.uscis.gov/portal/site/usc...00082ca60aRCRD