I’ve sat w a controller and I kept a log for the calls but they were the back-up for the JJ sheets.
A tip - for score runners. Always eyeball the sheets when you pick them up to look for empty lines. Easier to catch it while at the fence.
And JJ’s always write a brief description of horse/rider for some memory recall and to back up any comments you enter for any inquiries.
Most controllers have a magnetic board and some magnetic pieces that they move around on the course for where the two horses are on course (one on 1st 1/2, other on last 1/2). And count refusals.