What is the correct pressure for wearing the chin / face strap post neck, chin, cheek liposuction?

For my patients, when used,  the elastic chin/face garment should be comfortable with just mild elasticity felt. 

There's no evidence that compressive garment helps the final outcome of liposuction. Mostly it's for comfort. There's no reason for it to be placed so that it is uncomfortably tight.

Different surgeons may have different pressures that they prefer for patients to wear their chin straps after liposuction.  The simple answer is that it should be tight enough to keep some pressure but not so tight as to be uncomfortable.  I would recommend returning to your surgeon's office so that they can show you how tight they prefer the strap to be.