Bars in brake disc after only 700 kilometres

Hello, my junior has bought a new Leon FR 2.0 TDI. It is a day registration from 2016 with 9 kilometers on the clock. Now we have found that the brake disc at the front left has already strong bars. The vehicle is currently carefully driven over BAB and LS (approved on Friday and up to now 700 kilometers run). Since the brake has never squealed and it is several bars, it cannot be about foreign bodies like Steinchen as Ursach I would be interested to know if this lack had occurred several times. Next week I will go to the workshop and have an argument more in bed if they want to start to weigh the matter off. Thank you for reading and in joyful expectation of answers 🙂