meaning of the code

I have this code, and would like to know what the numbers mean:

 Private Sub wikipdf_Click()
    p = "D:\Formula\"
    f = "Inventory.xls"
    s = "Inventory"
    Application.ScreenUpdating = False
    For r = 1 To 500 <-----------------------------------------------------what does this numbers means?
        For c = 1 To 12 <---------------------------------------------------what does this numbers means? 
            a = Cells(r, c).Address
           Cells(r, c) = GetValue(p, f, s, a)
        Next c
    Next r
    Application.ScreenUpdating = True