I don't think that part is accurate.
My reading of his statement suggests none of the data when she sent it was so marked at the time she sent it. He distinguishes classified by responsible authorities which often occurs after it is seen by top officials but before it is finalized as classified by the responsible agent.
https://www.fbi.gov/news/pressrel/p...lary-clintons-use-of-a-personal-e-mail-system
From the group of 30,000 e-mails returned to the State Department, 110 e-mails in 52 e-mail chains have been determined by the owning agency to contain classified information at the time they were sent or received. Eight of those chains contained information that was Top Secret at the time they were sent; 36 chains contained Secret information at the time; and eight contained Confidential information, which is the lowest level of classification. Separate from those, about 2,000 additional e-mails were “up-classified” to make them Confidential; the information in those had not been classified at the time the e-mails were sent.
My reading of Comey's statement is that the 110 were properly classified at the time they were sent. There were another 2,000 that were classified at a later date.
So she may have played a bit fast and loose as the state Department seems to often do, but. she apparently acted within the existing culture.
Not sure that should be an acceptable excuse or particularly laudable.