Meta Business Help Centre
Why amount spent is different in account spending limit, Ads Manager and billing history

Once you've set up an account spending limit, you can see a real-time estimate of the amount that you've spent towards your limit in your payment settings.

The amount spent here doesn't include any amount that you've spent on ads before you set up your limit. It just shows what you've spent since you created or last changed your limit. This is why the amount here may differ from the lifetime amount spent of your account or what you see in the Billing section of Ads Manager.
Note: Your account spending limit is different from your lifetime budget and billing threshold. The lifetime budget controls how much an ad set can spend over its lifetime. The billing threshold determines when you're charged for your ads.
Amount spent in Ads Manager
The amount spent in the Account overview section of your Ads Manager lets you see the total amount of money that you've spent across all your campaigns during a time period that you choose. Bear in mind that this is also an estimate because it can take up to 48 hours for ad results to be processed.

Charges in the Billing section of Ads Manager
When you make a payment for your Facebook ads, the transaction appears in the Billing section of your Ads Manager. Every transaction includes a receipt that shows details about your payment. The details include the amount that you've spent, the reason why you were billed, the campaigns that spent money and the results that your ads got you. You can view your ad charges and payment history for more information.