Hi anonymous user,
You can query for whatever you would like, including date ranges as well. Where are you getting those numbers for 20 or 50?
Note that there's a new notable events dashboard experience as of last year and the one in the blog you linked is outdated, but you can still use the custom queries. https://video2.skills-academy.com/en-in/azure/security-center/security-center-features-retirement-july2019#events-dashboard---the-new-experience