My amount received is more than amount invoiced?

I noticed when looking at my dashboard that the amount I have recieved so far this month is more than the amount invoiced.
Is there a way to see where the amount that hasnt been invoiced is coming from?
I’m a bit confused because all my invoices have been paid, I have a feed to my paypal account and everything is tagged so I can’t understand where the extra revenue is coming from.

This is not unusual as the payments you’ve received this month probably apply to invoices raised in the previous month(s). The amount invoiced and paid month by month would only be equal if all your customers paid their invoices in the month they were issued.

If you click the figure for the amount received it will drill-down on all payments received in that period and it will show which invoices they are linked to.