This is according to public comments by FBI Director James Comey. Three of these were not included in the emails Clinton turned over to the State Department, but were discovered by the FBI through other means. (Federal Bureau of Investigation, 7/5/2016)
The New York Times comments that this means those emails “should never have been sent or received on an unclassified computer network — not hers, not even the State Department’s official state.gov system. That fact refutes the core argument she and others have made: that the entire controversy turned on the overzealous, after-the-fact classification of emails as they were being made public under the Freedom of Information Act [FOIA], rather than the mishandling of the nation’s secrets.” (The New York Times, 7/5/2016)