Good evening Sarah and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We are sorry to hear about the tooltip being truncated on your site.
I would love to help you with this topic.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Secondly, if I am not mistaken, the tooltip uses the same excerpt rules as the WordPress excerpt.
You can read about this here: https://theeventscalendar.com/the-trouble-with-excerpts/
That way you could at least control what is displayed.
To further customize the tooltip, you will need to use a template override or a custom function.
You can read about that here: https://theeventscalendar.com/customizations/
More specifically, You might want to read our Themer’s guide to get a sense of how that works.
If coding is not really your cup of tea, you could always hire one of our recommended customizers to do the customization for you.
Let me know how that goes.
Best regards,
Geoff B.