Facebook has a slight delay from when a donation is made to when it is available to view in the Facebook Transaction data. Typically this is as follows:
Facebook Multi Day Transaction Reports
On any given day you can usually request a Facebook Multi Day Transaction report from Facebook for the day before yesterday.
The best way to think about this is if Fundraisers/Donations happen on a Monday, you can get the data on the Wednesday. If they happen on a Tuesday you can get the data on a Thursday and so on.
Facebook Data Importer (Single Day Importer)
With the Facebook Data Importer, there is usually a one day delay in Facebook making the data available.
This means if a Fundraisers/Donations happened on a Monday, you would be able to import this data using the Facebook Data Importer on the Wednesday.