How to get rid of empty blue row in LE dashboard table component?
And before we lose track of how it looked like in Spring 2018, below is a sample Table Report which does not have any "first column showing numbers" or any "blank row at the bottom" of the report either in the report or the dashboard as seen in your screenshot from Summer 2018.
This issue definitely is with Summer 2018.
Actual Report
When viewed on Dashboard