Smart Lipo on upper arms. What part of the arms is typically considered one area?

There is no consensus between surgeons that defines an official arm area for lipo. An expert will usually recommend complete treatment of the entire aesthetic area or unit that requires treatment for a pleasing and harmonious result. If there is fat in the axillary region, reducing it with lipo usually benefits the overall result of an arm liposuction irrespective of how the areas are defined by the surgeon.

The "arm" is a single area--the upper arm.  Fat on or around the chest (near the armpit), not on the arm, is a separate area.  Just discuss your goals with your surgeon, and she should be able to guide you.

The arm is generally considered an area.  Fatty tissue just above the breast into the shoulder or above the bra in the armpit would be extra.Discuss with your plastic surgeon.

Generally, the definition of "area" appears to differ from practice to practice.  This is unfortunate, especially when you are shopping around.
For upper arms, we typically include any areas that need sculpting and fat removal, and make sure that the transition to the surrounding areas is smooth and not abrupt.  This is a common mistake that is made by inexperienced surgeons and makes the area that has received lipo look obvious, rather than smooth.  For example, if you are receiving lipo on the upper arms, it is important that the surgeon also blend in the results with adjacent areas so that the results look very natural.
Ultimately, an experienced surgeon will know this and discuss it with you.  Make sure you see plenty of before/after photos during your consultation.
Good luck!

Our practice typically considers arms to be a unit extending from your elbow to the area just in front of your armpit. The treatment area is normally the underside of your arm where your triceps muscle is (ie where batwings form). If a patient has a small area of concern outside of this, like the bra roll or upper pectoral area, we may do this on a case-by-case basis to achieve a better cosmetic result. It is worth clarifying during your consultation as it will differ among physicians.