“Assuming you’re right …”

The phrase “assuming you’re right” is often used to indicate uncertainty or skepticism about a statement made by someone else. The acronym IFSO stands for “If and Only If,” which is a logical statement indicating that two conditions are equivalent. Taken together, the crossword question is asking for a phrase that means “If and Only If you are correct,” or a statement that only holds true if the preceding statement is accurate. In other words, the phrase “assuming you’re right” implies a conditional relationship between two statements, and the use of IFSO further emphasizes the importance of that relationship.