Create a Customer Invoice representing your Q1 Sales, for example $18,500.

Create a Vendor Bill representing your Q1 Expenses, for example $8,300.

Using the Documents App, create a new Odoo Spreadsheet based on the template provided:

With Q1 data created, your Spreadsheet will look like this:

Now, add Q2 Income (ie: $19,900) and Q2 Expenses (ie: $9,255):

Now, add Q3 Income (ie: $21,032) and Q3 Expenses (ie: $10,000): 

Be sure to understand which of the cells are dynamically generated (Actuals, Perf), and which are updated via this Spreadsheet by the User (Budget).

This template is hard-coded to use two specific Accounts on the Chart, be sure to understand how to create Spreadsheets from PIVOT tables in Odoo, and how FILTERING works:

Finally, if you have several Invoices in a particular quarter, you can right click on the total that is being calculated and see the records that are the basis for the calculation:

Resources for learning about Odoo Spreadsheets: