From what i see, your loop is driven by the "5" cell, so when input < 5 you keep decrementing past 0 and it wraps to 255. Drive the loop with the input cell instead. Stop when input hits 0, then check what's left in the "5" cell.

Tiny Brainfuck core (cell0 = numeric 0–9, cell1 = 5):

<+++++        set cell1 = 5 (assumes youre on cell1; adjust moves as needed)
<             back to input (cell0)

[             while input > 0
  -           input--
  >-          five--
  <           back to input
]

>             now on five
[             if five > 0 => input < 5
  /* MENOR */
  [-]
]

<             back to input
>             go to five again
<[            if five == 0 => input >= 5
  /* MAIOR */
]>

If you're reading a digit, subtract 48 first to get 0–9, then try running this