Bug? [SOLVED] Numberformat Output Wrong Value

#Region Project Attributes
    #AutoFlushLogs: True
    #CheckArrayBounds: True
    #StackBufferSize: 300
#End Region

Sub Process_Globals
    Public Serial1 As Serial
End Sub

Private Sub AppStart
    Serial1.Initialize(115200)
  
    Dim datetimestamp As ULong = 20250530
    LogULong(datetimestamp)
'    >>>
'    1 datetimestamp=20250530             
'    2 datetimestamp NumberFormat=20250530    <-- OK

    datetimestamp = 20250531
    LogULong(datetimestamp)
'    >>>
'    1 datetimestamp=20250531
'    2 datetimestamp NumberFormat=20250532    <-- BUG? 20250531 converted to 20250532
  
    datetimestamp = 20250532
    LogULong(datetimestamp)
'    >>>
'    1 datetimestamp=20250532
'    2 datetimestamp NumberFormat=20250532    <-- OK
End Sub

Private Sub LogULong(value As ULong)
    Log(">>>")
    Log("1 datetimestamp=", value)
    Log("2 datetimestamp numberformat=", NumberFormat(value, 0, 0))
End Sub

Dim ValueULong as ULong
' Check if value not exceeding Long max value
If ValueULong <= 2147483647 Then
  Dim ValueLong As Long = ValueULong
  Dim s As String = ValueLong
End If