Need help adjusting VB macro for appending data to rows with matching index numbers

Hello-

I have a macro that was written for me by someone awesome on this forum, however, our data has changed slightly and I cannot figure out how to adjust it.

We use a program that outputs data onto a spreadsheet. The same mouse is in a box for five minutes, but the program creates a separate row for each minute. Instead, the macro was designed to check the mouse ID in column C, and then move all of the following matching entries into the same row, in order.

The macro is working, but is not capturing all the data it should- there are five missing entries. I've attached the macro and a copy of the data below.

It would be really nice if someone could explain how this works a bit in case I need to edit things in the future so I won't have to bother anyone.

Sub FC3()

    
 Dim aNum, b
 Dim i As Long, ii As Long
 With ActiveWorkbook.ActiveSheet
    With .Range("a5:m" & Cells(Rows.Count, "c").End(xlUp).Row)
        aNum = .Value
        .Clear
    End With
    With CreateObject("Scripting.Dictionary")
       .CompareMode = 1
       For indx = LBound(aNum) To UBound(aNum)
           If Not .Exists(aNum(indx, 3)) Then
               ReDim b(1 To UBound(aNum, 2))
               For ii = LBound(aNum, 2) To UBound(aNum, 2)
                   b(ii) = aNum(indx, ii)
               Next
               .Item(aNum(indx, 3)) = Join(b, ",")
           Else
               ReDim b(1 To 6)
               For ii = 1 To 6
                   b(ii) = aNum(indx, ii + 7)
               Next
               .Item(aNum(indx, 3)) = .Item(aNum(indx, 3)) & "," & Join(b, ",")
           End If
       Next
       aNum = .Items
    End With
    Application.ScreenUpdating = False
    For i = LBound(aNum) To UBound(aNum)
       x = Split(aNum(i), ",")
       For ii = LBound(x) To UBound(x)
           .Cells(i + 5, ii + 1) = x(ii)
       Next
    Next
    '.Columns("N:N").EntireColumn.Insert
    Application.ScreenUpdating = True
 End With
End Sub

Attachment 235963

Your help is greatly appreciated!