Centre In LIne Spare Holder #90956500

Hi can anyone help me with where the top holder (the part that sits on top of the tyre) fits under the seat. The item I have been sent does not have a loose plate with a hole in as per photo on webshop but it has a welded bracket with a tube type slot which is unwleded at the end and I cant figure out where to fit this piece under the seat? Cheers