15.78.13  PLUS 

Adds the value to the coordinate.  If you specify ERROR and you are adding
a  constant  to  X,Y,  or  Z  the  DX,DY,  or  DZ   are   also   modified.
DY=SQRT(DY**2+(e)**2) where e is the specified error.
                                  example
To add 2+-0.1 to y
     Y=Y PLUS 2 ERROR=.1
          or...
     Y=Y + 2 ERROR=.1