How does village expansion work?

I’m trying to build my own village, and for that I need to have sharp knowledge of village mechanics that the online documentation does not provide sufficiently.

I know that points of interests (beds, job blocks, bells) in the area of the village expands its boundary, but I don’t know how it works exactly.

If there is 1 bell, and 1 bed 20 blocks away, what will be the result? Does a new point of interest increase the total radius of the village, or does it create a new area of 32 blocks by 32 blocks? Will the village now be 52 blocks by 52 blocks or 32 blocks by 52 blocks?