Number of sub-tasks based on status
Return the number of sub-tasks in the Done or Complete statuses.
Configuration
Create a Custom smart number field and use the General parsing mode.
Expression
%{count(filterByStatus(subtasks(), "Done, Completed"))}
Please, note that by changing "Done, Completed" into other statuses and resolutions you can adapt this use case for your needs.
Format
Default
Used parser functions
The links lead to the JWTC documentation because the parser functions are shared functionalities.