[Husker] penalties in the red zone

[C Jolly]

I have a question about the rules in football brought on by watching the 
Colts vs the Steelers.

The Colts had the ball 3rd and goal on the 1 yard line (or 
thereabouts).  An offensive lineman moved and the ball
was moved back 5 yards.  So far so good.  Then a Steelers player was 
called for encroachment.  Instead of moving the
ball back to the 1 (a 5 yard penalty), they moved it halfway to the 
goal.  I always thought that a penalty that would cause
the ball across the goal line either way was moved halfway to the goal 
line.  If the penalty doesn't move the ball across the
goal line then the full penalty is inacted. 
    For example this is what I thought the rules were:

    Offense is on the defenses 7 yard line.  Defense has  an offside 
penalty.  The ball goes to the 2.
    Offense is on the defenses 4 yard line.  Defense is offside. The 
ball goes to the 2.
    Offense is on the offenses 8 yard line and they commit a personal 
foul.  The ball goes to the 4 yard  line.
     Offense is on the offenses 16 yard line and commits a personal 
foul  Since the penalty doesn't cause the
ball to go across the goal line, then it should go to the one.

    Can someone expalin where my thinking is wrong?

Thanks