In order to configure your account with either Recharger, BRAG or Balancer, Mayday needs to synchronise the data it has with what's in your Xero organisation for each connected entity.
If you want to use Mayday for previous months, choose the start date as the first month that you want to use Mayday for. The further back you go, the longer it will take to pull the data from your account.
Mayday automatically syncs with Xero daily and every time you log in, however, if you’d like to sync whilst you’re using the software, to reflect a recent change or ensure your information is up to date, simply press Sync in the left-hand menu and it will begin to sync.
Sync'ing can take some time, so it will run in the background and send you a notification when it's finished.
What does 'partial sync' mean?
A partial sync is simply a sync of data where not everything was able to be pulled in from Xero at this time. It might simply be because the amount of data being pulled has hit the Xero API limit.
This is most common on the initial sync when you first setup your Mayday account, as the amount of data being synced is significant (depending on your Xero org, and start date selected).
Either way, a partial sync will usually resolve itself the following day when the limits reset.
If you're really unsure, you can always can always contact Mayday support who can look into it further.