The Last Evaluation column refers to the last time the policy was evaluated on whether or not it should trigger:
The time designated in this column is not related to the time specified in a policy. The platform goes through all policies and checks to see if the policy should fire every 15 minutes. If the evaluation time matches up with the time specified in the policy block, the policy will fire. If the evaluation time does not, the policy will not fire.
NOTE: The evaluation time will still update on that policy page. So you can think of this column as the last time the platform evaluated whether or not we should trigger the policy; NOT if it was actually triggered.