what did I wrong?

[bb]

the b and c should be 2 and 3 on string 5. Instead they show 7 and 8,
even with predefined string 5.

I  kindly ask for help.

Kind regards BB

  
\version "2.18.2"

#(set-global-staff-size 27)             %%% System
  
   fourth = \stringTuning < f, a, d g c' f' >
  
   Scale= {
          \relative c'
    \override Score.BarNumber.break-visibility = ##(#t #t #t)
    \time 4/4
   {f, g, a, b, | c d e f | 
    c\5 d e f |   % with string definition
     g a b c' |  d' e' f' g' | a' b' c'' d'' |
     e'' f'' g''  a''
         \bar "|."
    }
   }
   
    \new TabStaff \with {
    \tabFullNotation
    \stemDown
    tablatureFormat = #fret-number-tablature-format-banjo
    stringTunings = #fourth 
    }
    {
      \Scale
  }