I have started doing NDB holds and the principle seems straight forward, but I cannot get my head around crosswind calculations. The Thom book 5 says to use 3x allowance and my instructor suggests 2x allowance and has a way of referring to the face of his watch to calculate this.
The proven method is 3xdrift if the wind is from the holding side of the beacon. 2xdrift if the wind is from the non-holding side. Finally 2xdrift if the resultant 3xdrift is within 30deg of the wind (head or tail).
The basic principle is that if you never want to overshoot the inbound track as it is difficult to get back on it, but if you are wide, holding off on the inbound turn is easy.
Re-clarify with your instructor for the conditions at the time and see if this is what he was referring to.