We use Balance database to store your account balance history on a daily basis. Both Balance and Bank accounts database are automatically generated the first time you connect your bank account, but you can use any other database with compatible properties.
Here are the values (both required and optional) used by Balance.

Number property type. It’s used as the balance amount.Date property type. It’s used as the date of the balance amount. In coming updates this will enable us to show you a line chart of your balance evolution.Relation property type. It’s used as the account where the balance come from.Bank accounts
Balance database