adjust displayed titles in the widget?

I’d like to include the posts’ series part number in the titles. The widget shows

first title
second title
third title

and I’d like to get something like

1. first title
2. second title
3. third title

I thought “Latest Series (inner tags):” might do it, but I apparently mis-understand what that’s for.

https://www.ads-software.com/plugins/organize-series/