If you activated your account a few days ago but the total backup size is still less than the size of your Gmail account, then most likely it is still backing up.
Depending on the size, it can take several days to back up the entire account. Google imposes a 1.5GB/day limit to the amount of data Backupify/Datto SaaS Protection for Google Apps is able to pull and will cut off IMAP access to your account if that threshold is crossed. As a result, larger Gmail accounts can take days to complete the initial backup.
Once the initial backup completes then the subsequent incremental jobs will complete much faster as they are only pulling over new and updated records.