From the press conference:But how many were "marked" classified?
"Only a very small number of the e-mails containing classified information bore markings indicating the presence of classified information. But even if information is not marked “classified” in an e-mail, participants who know or should know that the subject matter is classified are still obligated to protect it."
Also, the statistics are crazy. From the group of 30,000 e-mails provided by Clinton to the State department:
8 e-mail chains Top Secret at time of sending (including 7 that are Top Secret/ Special Access Program)
36 e-mail chains Secret at time of sending
8 e-mail chains Confidential at time of sending
2,000 e-mails "up-classified" to Confidential (they were not classified at the time of sending)
2,000 e-mails is a little over 6.5% of the work e-mails she ran through the server, not counting personal deleted e-mails. Also note the description as e-mail chains not just e-mails, meaning the that for each of those instances classified data was transmitted more than once on an unsecured system.