how to deal with old transactions and clearing them

I just downloaded Quicken and put my checking book data for the last 3 years into the system - went in easily. But how do I reconcile all the old data that has already been reconciled previously manually? I noticed these checkmarks in the Clear column. Does the checkmark mean it is cleared or does it need to be checked and removed? Since they all showed up with the checkmarks, does that mean they all were cleared as they entered?