In the Array Aggregator’s column field (wherever you want to map the numdoc variable),
You can use the built-in function replace to remove everything except numbers.
e.g.:
{{ replace(1.variable; "/\D+/g"; emptystring) }}
(paste directly in the field)
For more information, see the function documentation in the Help Center.
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Did you know, the concepts of about 70% of questions asked on this forum are already covered in the Make Academy. Investing some effort into it will save you lots of time and frustration using Make later!