ASDR = TODR (1 Eng Inop at VEF)
The variation in 1 second and 2 seconds diff between Vef and V1 depends upon when the aircraft was certified. 2 seconds is now the requirement, BUT (and it's a big BUT) due to the "Grandfather Clause" aircraft certified before the regulatory change are not required to be re-certified......and that accounts for most of the aircraft currently flying.
Balanced Field is a nice theoretical concept for an ideal world, in practice variation between Stopway and Clearway length put it in the back corner and Accelerate-Stop and Continued Takeoff situations considered separately will give the optimum field performance. Still...a useful tool for creating general Takeoff Charts / Tables (Most FMCs use it).