Hi Andrei,

Here’s the help description from IFS:

Post Actual and Recognized Revenue Difference
If this check box is selected the difference between actual revenue and recognized revenue will be posted separately as follows:

• if the recognized revenue is greater than actual revenue, the difference will be posted to posting type GP22
• if the recognized revenue is less than actual revenue, the difference will be posted to posting type GP23

Basically by enabling the checkbox, the difference between the invoiced revenues and the recognized revenue via project can be posted against the Posting Controls GP22 & GP23. This allows for more flexibility in the postings, an example is if your organization’s accounting policy is to practice conservatism where underbilled projects can be recognized as revenue (GP23 to revenue) but excess billings shouldn’t be recognized (GP22 to deferred revenue). 
 

Hope that helps. 

Robert