Default Settings
Monto makes this easy by allowing you to set the default number of reviews that are displayed in all review widgets across your site.
In Monto, go to Reviews > Customize and edit the option called "Reviews per page" on the right toolbar.
Save your changes and you're set!
(it might take a few minutes for this to update on the site)
Widget Specific Settings
If you want to set a different number to display for a single widget, you can do that as well.
Simply add this code to your review embed script to set the number:
data-reviews-per-page="3"
Just replace the "3" with whatever number you want to use and re-publish your site.