Use case
Count the number of issues in the same version as the current one.
Configuration
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
Parser expression
Add the following expression:
count(issuesFromJQL("fixVersion = " + %{00074}))
Once configured and added to an issue screen (e.g. an epic), the result will look like this:
If you still have questions, feel free to refer to our support team.