SyncApps always tries to sync only modified data between your software applications. This method is a best practice rather than trying to sync all data each time you run your SyncApps.
Let's face it sometimes the APIs of different software applications go down so you might not have your marketing Lists populated in time or you need to true up your CRM to your Marketing Automation solution.
If all of your data needs to be re-synced, at any time, please click on the "Reset Sync Process" button and during the next sync process, all your data between your software applications will sync.
*Please note - you will not lose your previous settings in your Sync Profile.
What's the difference between the "Sync Now" button without tapping the "Reset Sync Profile" button?
Pressing Sync Now will sync all data anytime you need to yet the schedule will accomplish the same thing just it runs automatically without logging into SyncApps.
For Reset Sync Process this feature will look at both systems anew and without looking at cached emails in the system to then match up each again so you can see a full report if you like anytime by using this feature as by default after the first sync runs we only sync changed data based on the timestamp of the record in both systems.