Hello there, knackservices.
Reports are transaction-based and look into the dates when it was recorded. To get the monthly data, you can record the transaction on a monthly, weekly, or daily basis. Ensure that the accounting method is also set to Accrual basis to see the possible income for the month.
Moving forward, you'll want to use the Progress Invoicing feature that lets you split an estimate into as many invoices as you need as you complete the work. Feel free to use these links that will help you manage your sales:
Keep me posted if there's anything else that you need. Take care!