It can be hard to identify which listtemplate you are trying to harness so it makes sense to go direct to the source and identify the right listtemplate by interrogating the list template associated with Heading 1.
I assume you already have the correct template attached so there is a faster way to import the styles from the attached template too.
Code:
Sub ScheduleUpdateStylesFromTemplate()
Dim x As Long, aLT As ListTemplate
Set aLT = ActiveDocument.Styles("Heading 1").ListTemplate
x = aLT.ListLevels(1).StartAt
ActiveDocument.UpdateStyles 'reimports styles from the attached template
aLT.ListLevels(1).StartAt = x
End Sub