Same as Bryan here, I was trying to understand what they are advising in that statement.
Presumably you've got the strobe type that you disconnect the plug cap and put strobe between cap and plug? If so, try putting it on the opposite lead from the same coil ie swap from 1 to 4 or the other way.
Again, as Bryan, the HT is coming from opposite ends of the same coil so differs between the two plugs, I don't know if this is what they mean.
The strobe with inductive pickup differ from the above by having the unit powered from the vehicle battery, and a clamp that goes around one of the HT lead to read the pulses going through to the plug without disconnecting it. This could be what they mean as Bryan states by flipping the clamp over. Don't think it applies to your strobe though.
I feel they make a good system which is well regarded, but if it's not quite right then hard to interpret with the information they aren't willing to disclose.
It's all well if the fit and performance is ok but hard to decipher if not.