In the image below, % of the next slide to show is set to "Do not show upcoming". As you can see there is nothing following the 3rd slide (blue squiggly line at the right-hand side).

In this image below, % of the next slide to show is set to "20%". As you can see there is a preview of the next slide following the 3rd slide (blue arrows at the right-hand side). The width of the preview increases or decreases with your % choice: 10%, 20% (shown), 30%.

Step 1: After you log in, click on Calendars (brown box below).

The Your Calendars page will open.

Step 2: Choose the slider view calendar you wish to modify (brown box below).

Step 3: Click on Design (brown box below).

Step 4: Click on Slider (brown box below).

Step 5: Scroll down until you find % of the next slide to show.

Click on the downward arrow (brown arrow below) to open the dropdown menu (brown box below). Click on your choice.

Click Save at the bottom to save your changes.