The goal you are looking for is about 400 rounds away if you have 100 in now. Your average, as a legend is based on your 500 best rounds as a Legend, it will not stabilize until you have 500 rounds in, then as you shoot a score that is lower than your highest score it will drop the highest score and add the lower score to recalculate your average. Until you get your 500 rounds in, every score (ranked round)is considered in calculating your average.
Actually, I just looked at your score history and it shows that you have 195 rounds showing as legend, and your history didn't go back to the time you made legend so you are closer than you think.