I Had Ultherapy Done Under my Chin and the Next Day I Had What Appeared Small Burnt Marks, is This Normal?

It is not necessarily "normal" to have redness or small areas that look burned after an Ultherapy treatment, but it can definitely happen. Most of the time they resolve within a week or so on their own (like yours did) and you do not need to worry about them.

Depending on the patient's skin type, they may have some redness after treatment since there is a good deal of focused ultrasound energy being delivered to the soft tissue layers deep to the skin to stimulate collagen production. The ultrasound transducer does not get hot at the surface, so there is very little risk for a "burn". Your experience, although not typical, it is also not unheard of.