What is the difference in effectiveness between 300 and 400 shots of Ulthera, and how many shots are safe if I am worried about sunken cheeks?

I don't naturally have a lot of facial fat, but I feel like my jawline and deep cheek fat are sagging slightly, so I am considering Ulthera.
Some people around me say that 300 shots are enough, while others say that if I'm going to do it anyway, I should hit at least 400 shots for the effects to last longer, so I am deeply conflicted.
Since the area below my cheekbones is slightly sunken for my age, I am most afraid of the side effects of sunken cheeks or looking gaunt.
I've heard that you should adjust the number of shots based on skin thickness or fat mass. For a body type like mine that isn't very flabby, what is the standard tip size and number of shots?
I would like some tips on how to ask the doctor to specifically target certain areas during a hospital consultation to avoid failure.
I can't easily make a decision because I'm afraid that if I get too greedy and add too many shots, I might end up looking older.
I would like to hear honest reviews from those who actually debated between the 300-shot and 400-shot options and made their choice, regarding their experiences and satisfaction levels.
It is a procedure that is quite expensive, and I am worried about wasting money and suffering only side effects, so please tell me some criteria for making a wise choice.
I would also like to know if I can return to my daily life immediately after the procedure, or if I should schedule an appointment a few days in advance due to swelling or bruising.
I would appreciate detailed advice from those with experience.