请问这个问题的两段代码是什么原因导致结果不同

第一种：
Dim i As Integer, n As Integer
For i = 1 To 7
If a(i, 1) Mod 7 = 0 Then
n = n + 1
ElseIf a(1, i) Mod 7 = 0 Then
n = n + 1
ElseIf a(7, i) Mod 7 = 0 Then
n = n + 1
ElseIf a(i, 7) Mod 7 = 0 Then
n = n + 1
End If
Next i
lblFirst = n
For i = 1 To 7
sum = sum + a(1, i) + a(i, 1) + a(7, i) + a(i, 7)
Next
sum = sum - a(1, 7) - a(1, 7) - a(7, 1) - a(7, 7)
lblSecond = sum

第二种：
n = 0
sum = 0
For i = 1 To 7
For j = 1 To 7
If a(i, j) Mod 7 = 0 Then n = n + 1
sum = sum + a(i, j)
Next j
Next i
For i = 2 To 6
For j = 2 To 6
If a(i, j) Mod 7 = 0 Then n = n - 1
sum = sum - a(i, j)
Next j
Next i
lblFirst = n
lblSecond = sum

有人没？