Which capacity is the lowest among the galleries listed?

The capacity listed as 15 is the lowest among the options provided. In scenarios where multiple numerical values are presented, the one with the smallest figure is identified as the lowest capacity. Capacity typically refers to the maximum amount that something can contain or the maximum number of individuals that can be accommodated in a specific area. Since the other values (20, 31, and 32) are higher, they do not fit the criterion of being the lowest. Thus, identifying 15 as the lowest value reflects a clear understanding of comparative numerical values.