V beam spot size vs power? Had test are done 12 days ago and it is not significantly darker red then it used to be.

12 days ago I had a vbeam test area done. The area is now a significantly darker red than it used to be. I didn't have pupuric bruising after - this crept up a few days after the procedure. Pre-op, the doc told me that a smaller spot size will result in a higher power needing to be used. I'm just curious how this works? I chose a smaller spot size of around 5-6mm because I didn't want to vbeam healthy areas of skin - only the specific area that is red.