Toe board clearance is the distance between the pedal lever on the engine side of the firewall , and the floor where the round detachable pedal passes into the inside of the vehicle, ( think about the pedal hitting the sheetmetal every time you let the brake pedal go ).
If you have about 2 inches or 50mm of free play in your pedal , I would suspect that there is too much clearance between the brake shoes and the drums, a brake shoe adjustment would be in order,