it isn't possible. You could change the axis to be a Logarithmic scale, although this might confuse the dashboard users.
This link has two other suggestions:
You may not like the look, but you could make two separate charts, identical except that they have different ranges (0-20 and 21-60),
and then connect them in a dashboard. You may want to make the break between them more obvious,
so that the user can see what is going on.
You could add an action, so that if a user clicks on a bar that traverses two graphs, both of them are highlighted.
Please see attached.
207542break.twbx 10.8 KB
Thank you for your suggestion I will try this out tomorrow :-)