I am doing a project with using vuejs2 and bootstrap vue. I was asked to do the ui like this (just an idea of the ui):

Explanation of the part I stuck, I want to achieve a ui that have a header with column span 2 (like red part) and put 2 data under that header (like yellow part)
From the document of bootstrap vue, I know that I can hardcode the layout, but as I have to connect to the api, I wish to use (and have to use) the :item and :fields to do. Just like this:
<b-table
bordered
responsive
class="mt-2"
:fields="tableFields"
:items="tableData"
>
<!--
how can I do the ui in here
-->
</b-table>
I would like to ask how could I achieve the ui with b-table