Need to fill conditional cell values based on unknown number of rows

Hi,
I just started using VBA and macros today, so please be kind!

I have a set of data in column R, with an unknown number of rows that looks like this

Days Late
-28
150
3
16
41
.
.
.

and I have written a script to add an adjacent column "S". I want to fill column S with conditional values based on the value of column R, sorted into categories such as "On Time", "Less than One Month Late", etc. Here is what I have so far, it doesn't work:

Sub Open_Order_Days_Late_Category()
'
' Open_Order_Days_Late_Category Macro
'

'
    Columns("S:S").Select
    Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
    Selection.ColumnWidth = 50
    
    Select Case Range("R:R").Value
        Case 1 To 6
            Range("S:S").Value = "Less than one week late"
        Case 7 To 14
            Range("S:S").Value = "One to two weeks late"
        Case 15 To 30
            Range("S:S").Value = "Two weeks to one month late"
        Case 31 To 60
            Range("S:S").Value = "One to two months late"
        Case 61 To 90
            Range("S:S").Value = "Two to three months late"
        Case 90 To 9999999
            Range("S:S").Value = "More than three months late"
        Case Else
            Range("S:S").Value = "On Time"
    End Select
    Range("S1").Select
    ActiveCell.FormulaR1C1 = "Days Late Category"
    With ActiveCell.Characters(Start:=1, Length:=18).Font
        .Name = "Calibri"
        .FontStyle = "Bold"
        .Size = 11
        .Strikethrough = False
        .Superscript = False
        .Subscript = False
        .OutlineFont = False
        .Shadow = False
        .Underline = xlUnderlineStyleNone
        .ThemeColor = xlThemeColorLight1
        .TintAndShade = 0
        .ThemeFont = xlThemeFontMinor
    End With

End Sub

Can someone please help me fix this code to make it work?