Answer: Your friend only needs to have their total trading volume of $1500 for you to be eligible for the prize. It means that your friend can trade multiple times with different trading volume, as long as the total amount is $1,500.
However, please be noted that the validity of the reward is 60 days meaning that your friends must complete verifying his/her phone number and trade at least $1,500 during the 60 day-period from his/her sign-up day.