The Brake Cooling Sched is not as complicated as it is tedious.
Assume for purposes of simplicity landing weight to be maximum (54.8 on most models of the 400). Simplify it even more and use 55K. That's given on the 1st column. Then assume brake application at 140Kts speed, given on the top of the chart. Check out 40 deg C to get the highest value : 29.1 millions of foot pounds on sea level.
On the next table below, Adjusted Brake Energy w/ No Reverse Thrust, round-off your 29.1 value (to simplify for purposes of discussion) to 30. Locate it on the topmost row under EVENT. You'll get a value of 19.4 for Autobrakes 1 Landing.
Moving on to the Recommended Brake Cooling Schedule (Cat A), the value 19.4 shall indicate you falling under the CAUTION ZONE.
But if you again check max brake application below 100kts, you'd end up with adjusted brake energy of 10, and min turn-around time of 19 minutes ONLY.
Simply put, if you apply brakes below 100kts even w/o reverse, you can be sure you're gonna be within the minimum turn-around time.
Having idle reverse makes it even more so.
Cheers!
