The size of the canal is low normal on a congenital basis:
When people under the age of 50 have spinal stenosis, it is usually due to a genetic predisposition called congenital spinal stenosis, which means they are born with a small spinal canal. This can put pressure on portions of the spinal cord.
The conus terminates at T12-L1:
The spinal cord most commonly terminates at levels of L1-L2, but there is a wide range of normal variation. In your case, the end of the spinal cord known as conus medullaris terminates slightly higher than expected.