fix silly math error

        zs = process_axis(z_opt, z_values)

        zs = process_axis(z_opt, z_values)

        # this could be moved to common code, but unlikely to be ever triggered anywhere else

        # this could be moved to common code, but unlikely to be ever triggered anywhere else

        Image.MAX_IMAGE_PIXELS = opts.img_max_size_mp * 1.1 # allow 10% overhead for margins and legend

        Image.MAX_IMAGE_PIXELS = opts.img_max_size_mp * 1000000 * 1.1 # allow 10% overhead for margins and legend

        grid_mp = round(len(xs) * len(ys) * len(zs) * p.width * p.height / 1000000)

        grid_mp = round(len(xs) * len(ys) * len(zs) * p.width * p.height / 1000000)

        if grid_mp > opts.img_max_size_mp:

        if grid_mp > opts.img_max_size_mp:

            return Processed(p, [], p.seed, info=f'Error: Resulting grid would be too large ({grid_mp} MPixels) (max configured size is {opts.img_max_size_mp} MPixels)')

            return Processed(p, [], p.seed, info=f'Error: Resulting grid would be too large ({grid_mp} MPixels) (max configured size is {opts.img_max_size_mp} MPixels)')