What is the exact spawning area of an iron golem within a village?

I have created an artificial village and I know its center point. In the minecraft wiki, I find this information about the spawing area of iron golems within a village:

The golem spawning zone is a 16×16×6 area centered around the center point of the village.

Village mechanics wiki article

However, it is not clear to me where exactly this area is. The village center point is, as I understand, a coordinate like block has. But a 16x16x6 volume does not contain a center block.

In the following image, which colored pixel would be the village center? (view from top on the left, view from the side on the right)

Or am I totally wrong and the area is distributed around the center point like in the following image? (again, view from top on the left, view from the side on the right)

The coordinate system of the Minecraft world isn't centered on blocks. Integer values of a coordinate axis (i.e. "1", "2", "3" and not e.g. "1.5") are exactly between blocks. The center of a block is always a coordinate of the form "n.5" (with n some integer number). So e.g. if x and z axis are both at integer values (e.g. x=4 and y=8), then this point is not within a block, but on the very boundary of a block and is shared among 4 blocks (their corners). If the y-axis would have an integer value as well, the point would be shared among 8 blocks.

Most of the times (always?) when people (e.g. at the wiki) talk about coordinates, they mean this coordinate system (shown on the F3 debug screen). So the center of your 16x16x16 area is a single point, not a block.

In the linked article it says:

Both the center point and radius are rounded to whole numbers; It is unclear if they round up, down, or to the nearest integer.

If this is true, then your center point is always a point that 8 blocks share with each other on their corners. From there you extend 8 blocks in each direction to get your spawning area.