Those numbers can represent grill power or a control scale rather than a temperature in degrees. They should not be copied into an oven recipe as equivalent settings.
What the observation means
A separate grill and an oven have different heating purposes. Some grill controls also select half or full width. Read the complete markings rather than assuming every numbered knob works like a thermostat.
A useful next step
Use the grill's own cooking and door-position instructions. Record the scale position if its behaviour changes. Do not test maximum power repeatedly to discover what an unlabelled setting means or judge safety from the knob's number alone.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.