Modification of a field at the creation of the record with BPA

Hello to all,
I want to modify this field at the creation of the record with BPA ("Customer" screen, "Invoice" tab): 

So I created an EVENT, which triggers on the concerned table, at the creation of a new row : 

. and an action that triggers the BPA :

My diagram looks like this : 

And here is the configuration of my "IFS Projection" element.

When triggering the EVENT, I get this error message: 

I think that the configuration of my "IFS Projection" element is not correct. Indeed, using a tool like Postman, IFS calls this web service :  

It looks like IFS is calling 2 entity sets. Unfortunately I can't enter 2 in the BPA configuration.

Thanks in advance.