Vehicle Delta Slip Angle.

I’m trying to get the delta slip angle of vehicles by the formula number 16 found here:

In my understanding it is: mass / axle length * (Center of mass to Rear Axle distance / Rear tire stiffness - Center of mass to Front Axle distance / Front tire stiffness) * ay, which I totally ignore the meaning of.

Is there anyone good at physics that can help me? Is there an easier way to get the delta slip angle?