What Does MSF Indicate In Follicular Study?

Hi, I am 32 years old and have been trying to conceive for 6 months. I have a regular menstrual cycle of 28 - 30 days. My doctor suggested I go for Follicular study. Today was my 13th day and the follicular study showed Right ovary - MSF, Left ovary - 17 x 18 and The E.T - 9. What does MSF indicate? When am i likely to ovulate?