Going above 18740- BN indicates that choppy move down from 20310 is all done for wave-X in larger wave-(2) likely to start wave-Y which should finish the complete corrective sequence. This whole pattern becomes invalid once BN moves above 20576.
Trading Strategy
Going above 18740 shall open deep upside or below 17950 could give downside, but shall be limited- which needs to be checked again once it moves below.