Hi there,
Thanks for reaching out. I will try to help with your question.
It seems that your theme is overriding the calendar styles. They are supplying their own styles for tribe event calendar elements, so you will need to add some additional CSS if you want to modify the styles that come with your theme.
You can target the title with “.tribe-events-tooltip .entry-title” and the duration with “.tribe-events-tooltip .tribe-event-duration”
Hope that helps! Please let us know if you have any additional questions about this.
Thanks,
Sky