Exporting from some advanced searches exports too many records. This can be replicated in the Drupal demo system running CRM 1.7.9572. Here's how:
1) Do an advanced search under the Activity History section for the "Donation" activity type.
2) Select the "all 13 records" radio button, "Export Contacts" from the "more actions" menu, and click Go.
3) Keep the "Export PRIMARY contact fields" selection and click Continue
You will get way too many records, around 1068 records instead of the selected 13.
I am attaching a sample export file.