FiniteVolumeSolver error about time step

When running FV, there is this error. I use CFL=0.7. How to fix the warning or how does it matter to the code.

 if ( !tarch::la::equals(cellDescription.getTimeStepSize(), 0.0) && tarch::la::smaller(admissibleTimeStepSize,cellDescription.getTimeStepSize()) ) {
    logWarning("updateSolution(...)","Finite volumes solver time step size harmed CFL condition. dt="<<
               cellDescription.getTimeStepSize()<<", dt_adm=" << admissibleTimeStepSize << ". cell=" <<cellDescription.toString());
  }