fortran-column-ruler-tab

fortran-column-ruler-tab is a variable defined in `fortran.el'.
Its value is

"0       810        20        30        40        50        60        70\n[   ]|  { |    |    |    |    |    |    |    |    |    |    |    |    |}\n"

• This variable is safe as a file local variable if its value
  satisfies the predicate `stringp'.

Documentation:
String displayed above current line by M-x fortran-column-ruler.
This variable is used in TAB format mode.
See the variable `fortran-column-ruler-fixed' for fixed format mode.

You can customize this variable.