The Price Table Settings tool has two components, the left panel shows a mockup of the price table with some areas that you can click into in order to make changes, such as data labels, price table footer and the Section name; the right panel contains style settings that can be updated by clicking on one of the section-headings.
To adjust the border styles, click on the heading Table Line Styles
Next you will see the settings appear (as shown below). You can select the style of line by clicking on the Style drop down, the default setting is Solid - this will be a continious line. Other options are dotted, dashed and none (no lines).
To set the thickness of the lines use the Weight input, the default is 1 (pixel) to increase type a larger number eg, 2 or 3.
The line colour can be set to light grey or dark grey by using the colour drop down.
After you have made your changes, click on the Save button (top right of the page)