The GEO_PERFORMANCE_REPORT gives all statistics aggregated at the country/territory level. If other segment fields are used, you may get more than one row per country/territory. The
AdGroupName field is of type Segment behavior so you are getting the
one row
corresponding to each AdGroupName plus
CountryCriteriaId combination. Please check out
GEO_PERFORMANCE_REPORT document for more details.
Umesh, AdWords API Team.