Using your measurements, it's 200 based on the inside and 215 based on the outside. So, you were told wrong. Maybe they thought it was a 240.
I once dated someone who insisted she was 5-5, which I knew had to be false. She demanded I measure her and she was 5-2. Then she remembered that for many years to get modeling assignments she had gotten used to adding 3 inches to her height. Then after 10 years, she forgot it wasn't true.