Great question! I have seen it handled a few different ways. What is certain is that students should put and oval around the function definition of their algorithm (AND the two child functions should also be included in that oval) and a rectangle around the function definition for their abstraction.
There is no need to put ovals/rectangles around the calls to these functions. The most important thing is to have clear writing in the written part. If a student thinks a screenshot to the function calls helps make their point about how the abstraction manages complexity, then it seems like no points would be deducted, but again, it is not necessary. You can find this information in the Create Survival Guide too!
I will add this one to the AP FRQ list too since it is a bit on the unclear side when you read the AP docs.
Does that help?