Leuprolide Acetate Question

Ok ladies, frozen transfer question. Our frozen transfer is April 19. Today the doctor said to start 20 units of Leuprolide Acetate injections each evening while continuing birth control for the next week. After a couple weeks I still continue Leuprolide but change it to only 5 units. I guess I’m just confused because for my fresh transfer Leuprolide was taken only once as a trigger? What is it being used for this round? Just looking for some reassurance that this is normal and/or I didn’t misunderstand the doctor!