section .data
    value1  db   15
    value2  db   20
section .text
    global  _start
    
_start:
    mov al, [value1]
    mov bl, [value2]
    cmp al, bl
    jb  below
    
not_below:
    ; your codeing expertise takes spotlight here,(VALUE1 IS NOT BELOW VALUE2)
    jmp done
    
below:
    ; code cases where (VALUE 1 IS BELOW VALUE2)
    
done:
    ; exit related code