how to create a num question for Moodle with R/exams with partially correct answers

I want to use R/exams to create randomised Moodle questions. When I create - by hand - a num question in Moodle, I can add partially correct answers, for typical small mistakes, that I grade with 50%. I could not find something like that in R/exams. I can provide some XML of such a Moodle question if that is of any help.