[agraham]

Originally Posted by wolfgang

The only thing I do not understand is that label4.Text = n displays only even numbers

You may be getting two LocationChanged events each time and are being re-entered when you update the labels. You can check with some code like this.

ReEntry = false ' in Globals
...
Sub gpsint_GPSLocationChanged
  If Not(ReEntry) Then
      ReEntry = true
      If gpsint.GPSValid = true Then
        n = n + 1
        label2.Text = gpsint.GPSUTCTime
        label6.Text = gpsint.GPSSpeed & " [knots]"
        label4.Text = n
      Else
        label2.Text = "no fix, wait"
      End If
      hw.KeepAlive
      ReEntry = false
  End IF
End Sub