Is 10-20 minutes of a CoolSculpting application enough to freeze fat?

Hi. Thank u for your time. I was expecting the CoolSculpting treatment to take an hour per area but the esthetician only did 10-20 minutes per application explaining that I didn’t need more than that time, I had my lower back, arms and stomach done. She also explained that different areas of the body needed different times of treatment, like the arms only needed 10 minutes of treatment. My arms were very bruised after the ten minutes.