Timer Code : Doesn't Work Properly

Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick
        Dim A As Integer
        Dim B As Integer
        Dim C As Integer
        Dim D As Integer
        Dim X As Integer
        A = RichTextBox4.Text
        B = RichTextBox5.Text
        C = RichTextBox6.Text
        D = 1
        X = 59
        If A >= 0 & B >= 0 & C > 0 Then
            RichTextBox6.Text = C - D
        End If
        If A >= 0 & B > 0 & C = 0 Then
            RichTextBox5.Text = B - D
            RichTextBox6.Text = X
        End If
        If A > 0 & B = 0 & C = 0 Then
            RichTextBox4.Text = A - D
            RichTextBox5.Text = X
            RichTextBox6.Text = X
        End If
        If A = 0 & B = 0 & C = 0 Then
            MsgBox("Stop!")
        End If
    End Sub

RichTextBox4.Text is Hour

RichTextBox5.Text is Minute

RichTextBox6.Text is Second

Howevere it looks like -1,-2 on RichTextBox4, if I input 59 seconds.

Thank You.