The Sprout HR Database field is used to link the Sprout HR attendance to Sprout Payroll. This is how Sprout HR is able to export the correct attendance to process payroll.
The format is "Payroll_" followed by the company specific database code. This is actually the same code used when logging in any Sprout HR account.
For example, if the Sprout Payroll username is "ABC123\johnd", "ABC123" is the company specific database code that precedes the username "johnd" and all other usernames under that specific account.