If you merge every 4 cells in column A and then put some numbers in the merged cells (say 1 to 16), it will appear as though the number is at the bottom (depending on your formatting). However, it is actually in the first cell of each group of merged cells.

Try this little example:

Sub test()
For i = 1 To 64
    Debug.Print i; " "; Range("A" & i)
Next 'i
End Sub

It's also interesting that, if I put an Autofilter on and filter numbers less than or equal to 13, I only get the cells with the numbers, not the merged cell block.

However, there's a clue there. Try:

Sub test2()
    With Range("A1:A" & Range("A" & Rows.Count).End(xlUp).Row)
        MsgBox Application.WorksheetFunction.RoundUp(.Rows.Count / 4, 0)
    End With
End Sub

Just be wary of header rows confusing the count

Regards