The space between cap and elbow
In Robin, short integrated sleeves continue the off-shoulder draping across the fitted bodice. The result is a continuous sculpted band rather than a separate, flat sleeve. Samanta offers a contrasting example: gathered puff volume tapers into a shorter upper-arm length.
Look at the end point in a side view. A cap sleeve stops closer to the shoulder; a long sleeve continues down the arm. For short sleeves, the cut of the bodice and upper edge tells more than length alone.
Robin’s sleeves belong to an off-shoulder band that sweeps across the bodice. Samanta’s are separate-looking rounded forms below its off-shoulder neckline. The comparison is useful because both stop around the upper arm, yet one continues a draped line and the other creates a raised accent. Sleeve length alone will not tell you whether the shoulder feels smooth or full.
What matters at the fitting?
Lift and lower the arms to see whether the short sleeve stays in its intended position. Then turn sideways to judge its width against the waist and skirt. This is particularly relevant for integrated off-shoulder sleeves, which move with the upper bodice.