The "Action suppressed. File Sizes are different with same date." message can occur in a multi-directional Rule. This behavior is caused by applications that will modify metadata resulting in different sizes with the same modified time/date stamp. Older versions of PowerPoint were a common cause of this. If you look at the two files, there will be no visible difference.
In this situation, you have to instruct SureSync how you want the conflict handled. Expand the Job in question and click on the Rule. Click on the Options tab. From there, you have the option of "Log an error," "Ignore the difference," "Copy the larger file," and "Copy the smaller file.
Select the option you prefer and click apply. You will need to stop/start the Schedule or Monitor for the change to take effect.