Here's the full code. You lost me a bit there so run it and report back on what needs changing.
Sub x()

Dim nMinAP As Long, nMaxAP As Long, nStepAP As Long
Dim nMinAG As Long, nMaxAG As Long, nStepAG As Long
Dim i As Long, nLastcol As Long, nlastrow As Long
Dim rRow, rCol, rRef, j As Long
Dim rStart As Range, rData As Range

With Application
    .EnableEvents = False
    .ScreenUpdating = False
    .DisplayAlerts = False
    .Calculation = xlCalculationManual
End With

On Error Resume Next
Sheets("Charts").Delete
On Error GoTo 0
Sheets.Add(After:=Sheets(Sheets.Count)).Name = "Charts"

Sheets("Mov_Avg_Chart").Activate
nMinAP = Range("B22").Value
nMaxAP = Range("B23").Value
nStepAP = Range("B24").Value
nMinAG = Range("B25").Value
nMaxAG = Range("B26").Value
nStepAG = Range("B27").Value
Set rRow = Range("C8")
Set rCol = Range("C6")
rRef = Array("G7", "G9", "G10", "G11")

nlastrow = Cells.Find(What:="*", After:=Cells(1, 1), SearchOrder:=xlByRows, SearchDirection:=xlPrevious).Row
nLastcol = Cells.Find(What:="*", After:=Cells(1, 1), SearchOrder:=xlByColumns, SearchDirection:=xlPrevious).Column
If nLastcol < 9 Then
    Range(Cells(15, "I"), Cells(nlastrow, "I")).Clear
Else
    Range(Cells(15, "I"), Cells(nlastrow, nLastcol)).Clear
End If

Set rStart = Range("I15")

For i = LBound(rRef) To UBound(rRef)
    With rStart
        .Formula = "=" & rRef(i)
        .Interior.ColorIndex = 4
        .Offset(1).Value = nMinAP
        .Offset(1).DataSeries Rowcol:=xlColumns, Type:=xlLinear, Step:=nStepAP, Stop:=nMaxAP
        .Offset(, 1).Value = nMinAG
        .Offset(, 1).DataSeries Rowcol:=xlRows, Type:=xlLinear, Step:=nStepAG, Stop:=nMaxAG
        With .CurrentRegion
            .Rows(1).Font.Bold = True
            .Columns(1).Font.Bold = True
        End With
    End With
    Set rData = rStart.Offset(1, 1).CurrentRegion
    With rData
        .NumberFormat = "0.00"
        .Table RowInput:=rRow, ColumnInput:=rCol
        With .Offset(1, 1).Resize(.Rows.Count - 1, .Columns.Count - 1)
            .Select
            ActiveSheet.Shapes.AddChart.Select
            ActiveChart.SetSourceData Source:=Range("Mov_Avg_Chart!" & .Address)
            ActiveChart.ChartType = xlSurfaceTopView
            ActiveChart.Location xlLocationAsObject, "Charts"
            For j = 1 To rData.Rows.Count - 1
                ActiveChart.SeriesCollection(j).Name = rData(j + 1, 1)
            Next j
            ActiveChart.SeriesCollection(1).XValues = rData(1, 2).Resize(, rData.Columns.Count - 1)
            Sheets("Mov_Avg_Chart").Activate
        End With
    End With
    Set rStart = rStart.Offset(rStart.CurrentRegion.Rows.Count + 1)
Next i

With Application
    .EnableEvents = True
    .ScreenUpdating = True
    .DisplayAlerts = True
    .Calculation = xlCalculationAutomatic
End With

End Sub