All the maximum loading weights stated for our roof bars are dynamic loading limits, the weight that can be carried while the vehicle is moving. If you check the instructions for a particular set of bars you can see the maximum dynamic loading weight. You'll also need to check your vehicle's roof loading limit (check the vehicle handbook or ask your local dealer). Always be guided by the lower loading limit.
Static (parked) loading weights are relevant if, for example, you are carrying a roof top tent. This is typically in the region of 3 times the dynamic weight. Please note that roof top tents should only be fitted to vehicles with raised rails, flush mounted rails, fixing points or T-track channels - they are not suitable for use with plain roof vehicles, the type where the roof bars clamp around the bodywork.