This is Dr. Cyril Wecht's favourite piece of evidence.
As I understand it the bullet on the far right has been fired through the wrist of a cadaver. This is the closest the WC could come to a 'pristine' bullet that had passed through a wrisbone.
The SBT posits the bullet was no longer pristine by time it struck the Connally's wrist, having gone through Kennedy's neck and Connally's torso, making it slow down and tumble.
The cadaver test -- by showing how mangled a pristine bullet (one fired nose-on at full velocity) would look from just hitting the wrist bone -- was I think meant to demonstrate that CE399 must have not arrived at the Governor's wrist that way. Since then some tests have sought to duplicate the "non-prisitne" SBT path, with the Australian people coming close in the 2004 "Unsolved History" episode "JFK: Beyond the Magic Bullet".
BTW, the cadaver bullet might have struck the wrist bone more squarely, whereas CE399 might have simply slapped off the Governor's radius. Connally's X-ray doesn't show a hole through the bone, only fractures with the bone present.