To force the client not to backup all the files on the first backup, you will have to follow these steps.
Close the client, open registry and navigate to the following key.
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Quantum Tech, Inc.\Remote Backup\Settings
here change the value of "DisableFirstFull" to True.
This will work for Archive bit, for Modified date time you will have to follow this additionally. Ensure client is not running.
Locate the file named, BackupSetUp.ini from the client install folder (By Default C:\Program Files (x86)\BackupAddict) and open it, to that file add the key 'ModifiedDate" under NGClient and enter the date after which you wish the files to be backed up.
Now open the client and run a backup and check.