Moles are usually brown spots on the peach skin. Some others are only slightly darker than the surrounding skin while others are black like coal. Not all moles are in shades of brown, some moles are red while some are grayish.
On average there are more moles on the right arm than on the left, and there are more moles on the forearm than on the upper arm. On average there are slightly more moles on the front and outward side of the arms (side facing away from their torsos) than on the back side and least on the inward side.
Maybe left-handed people have more moles on the left arm on average than on the right. If it is correct, it can loosely determine the handedness of a person by comparing number of mole between two arms.
I estimate that most people have between 3-30 moles on one arm, and the number and sizes are about the same across two genders.
Because girls tend to wear t-shirts that have shorter sleeves than guys wearing t-shirts and wearing sleeveless shirts more than guys, girls would on average display more moles on their arms than guys, especially on their upper arms.
Most moles on girl's arms have diameters of 1-2 mm, while few measure as big as 8 mm. Moles stretch on average about 1/40 the arm width, some stretch for less than 1/100 the arm width while some others stretch as much as 1/8 the arm width. For example, a girl has a mole located on her mid-upper arm sizing at 2 mm on the arm having a width of 8 cm, meaning that mole is 1/40 the arm width. Many girls have a big mole just underneath the shoulder.
I wonder if there are moles so small that they can only be seen under a microscope. Or I may guess that moles can only go so small, down to the width of a human hair.
I believe that skinnier arms tend to have smaller moles but higher mole-arm width ratio since the relationship between mole size and arm width is square root. For example, her arms are 10% skinnier than the other would have average mole sizes around 5% smaller.
Presence and amount of moles do not influence the odor I believe. If you use a funnel-shaped tool with very small opening on the end touching the skin, then if you sniff at it using that tool with the end right on the mole, it would smell the same as if sniffing on the peach skin, no matter what color the mole is. But if she has a really big mole, you may not need that tool to directly sniff at that mole. Or in other words on girly girls, that brown skin surface would smell as girly as on the peach surface! So moles influencing the smell emitted from the skin is only a myth.