I think you misread. They stated specifically that every search is fully auditable. In NSA speech, that means that no audits of any sort are ever performed; searches are only auditable, never audited. This works similar to the collection of domestic data, which is siphoned off, stored, replicated and indexed, but never actually accessed by anyone.

(Some of the screenshots suggest that the legitimation for every search is entered into a free text field, making any kind of automated analysis extremely difficult. This already suggests that no such statistics are collected.)