Firstly, let me explain more about the rendering behavior of the data items. Like in your case, table's borders are rendered around it. This means that the bottom border will show right after the last row.
At the moment, there is no direct way to extend border lines to the bottom of the page. But a similar request is already approved for implementing - please refer to this post from our feedback portal. Feel free to vote for it as it can raise the priority of this feature.
A possible workaround to achieve the desired appearance is creating an image that imitates vertical lines extending to the bottom of the page and setting it in the report section's Style.BackgroundImage. Additionally, you can set a top border of the section that is used to display the footer information.
Another workaround could be used only if you know how many rows are retrieved from the dataset and how much space left. Then, add empty rows to the end of the dataset to bring the vertical lines till the end of the page.
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