Hello! J-scaled HMQC is a pseudo-3d experiment, obtained by adding additional spin-echo before acquisition. Scaling factor is a multiplier for this spin-echo delay, or you may leave this delay variable for 3d experiment. For further details look at http://www.sciencedirect.com/science/article/pii/S0040403900021274 there described hmqc experiments with both Jch and Jcc scaling.