Display the highest value out of several fields.
Create a new Calculated Number Field (by JWT) custom field and name it properly.
Providing a description will help you to identify what the custom field does but this step is optional.
Add the following expression after replacing the field codes with the corresponding ones.
max([{issue.cfaaaaa}, {issue.cfbbbbb}, {issue.cfccccc}, {issue.cfddddd}, {issue.cfeeeee}])
Add the field to the relevant view screens.
Remember: All calculated fields are read-only and cannot be manually updated on a create or edit screen.