Hi @AlexandraM,
the new Bar Chart nodes lack the functionality to automatically scale to 100%. You have to calculate that yourself I am afraid to say. Check out my post for a solution and upvote it so that feature gab gets close 
PS: I quickly created an example workflow for you and future Knimers as this question has been asked recently. If it is a suitable solution, I’d appreciate if you mark my post as one.
Best
Mike