It means that I will only make a certain number of prints in each size and then I will sell no more. I print a limited edition of each size print so there will only be 25 prints made in the 12x16 inch size, 30 prints made in the 17x23 inch size and 36 prints in the 24x30 inches size. [please see the next FAQ for the way that I measure my prints].
The more prints of a particular sized image that sell, the higher the price of each suceeding print or group of prints will be [I thnk my business friends refer to this as supply & demand]. At this point in the process of selling archival prints, I am not into the second tier of prices.