That is because 95-68=27. 27/2=13.5
You can see from the graph of the normal distribution.
Add them up. one below to two above would be 34+34+13.5=81.5
From the tables, look up z=-1 and z=2. You should get close to 81.5
z=-1 corresponds to .1587. Then, .5-.1587=.3413
z=2 corresponds to .9772. Then, .9772-.5=.4772
See?. Close to the graph method.