According to other owners, it usually refers to fluid in the transmission.
Apparently it counts how often the fluid goes above a specified temperature, and after a certain amount it tells you to get it sorted. Others had low fluid (leak), or burnt fluid (brown and stinky on the dipstick instead of red and oil-smelly).
As long as it doesn’t go into limp mode, i’d not be too concerned. I’d get it sorted of course, but i’d not leave the car parked until then.
In regards to paying, we got asked by SEAT to pay £12, to get the car picked up and brought back for service. After pointing out the fact that it’s an MB car, they just billed MB directly.
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.