At the end of every day, every supermarket calls him with the daily results. He writes them down, takes a picture and sends that to his manager at the national HQ.
He just uses his phone and the occasional meeting to do business, there is no computer/laptop or system on his end.
Aldi is always portrayed as brutally efficient. So I was wondering what to read into this. Best I was able to come up with is that it's cheaper for them not to have an overseeing system to manage this.