It is important to remember that application rates that are below recommendations may simply be a waste of foam concentrate and effort.
You may need to delay attack until sufficient concentrate and all needed resources are on scene and ready or ...
use what is available for exposures or rescue modes.

Application Rate is how much of that solution is applied in a specified time.
Application Rate IS NOT referring to 3%, 6%

There are five basic considerations
that will dictate the application rate/time:
1. Surface Size (Square Footage of surface)
2. Fuel Type (Hydrocarbon/Polar Solvent and what type polar solvent)
3. Fuel Depth (Surface only spill fire Vs. 1"-2" or greater)
4. Application time needed
5. Foam coverage disturbance (Wind, hostile flame damage, rapid convection columns) While not part of the math calculations, these factors may require more foam or frequent reapplication.

Just as a structure fire needs a minimum flow rate to suppress a fire, so does a flammable/combustible liquid fire.