Spawn chunk range?

So, when I calculated my maps spawn chunks I was getting a 10 chunks range from the spawn location in each direction rather than the 6 mentioned in many videos and sources in Minecraft.

I used a light sensor, hopper and chest to test redstone signals. After a short amount of night anywhere else when I return to the spawn during the day through a nether portal any chests that had items moved to them were getting a redstone signal at night and thus in the spawn chunks.