Share Setup Sync Direction
Accounts listed on the left side (marked as "Source") will send and receive changes from accounts in the same left column. Accounts listed on the right column will only accept changes from accounts on the left side (one-way sync).
If you want to setup one-way synchronization, put accounts from which data should be synced from on the left and accounts that data should be synced to on the right-side. In other words, data will be synced from accounts on the left to the accounts on the right column.
In case you want to setup two-way sync for all accounts, put all accounts on the left left side.