2 months discrepancy in previous job finish date and sterling background check

Hey, I am waiting for the sterling background check and I just realized I said that my contract with my last company ended in June, but was in April. To be honest, I put that in my resume because I worried about 5 months being a huge gap without working. Now I understand it was stupid. Should it be a big problem or two months gap is negligible. Other question:how they can check that? Calling your contact number for the company? Because it's a friend of mine and he can say that the date is true. What do u think?) Thanks in advance :)