A usual definition of a 'divergence' is when the difference between the respective values of two series (usually price and a certain metric) increase over time. In our case, one is the WT4D series of the frequency in question and the other series is the direction and/or position of the slower frequency. More concretely, the divergence (and GDM) is calculated by taking the peaks/valleys of the (🐇) normal series and compare them with the behaviour of the (🐢) slow. Or, for the other set, that is the (🐢) slow and (🦥) lethargic series respectively.
That 'behaviour' is what we set in this parameter. You can choose to define a divergence when the 🐇/🐢 waves are getting weaker, but the 🐢/🦥 series are going into the opposite direction (option 2). Another way is to choose the 🐢/🦥 series to be positioned above/below zero (option 3, default behaviour). Both of these can also be chosen (option 4), meaning that in bullish scenario the 🐇 series makes higher lows but the 🐢 is above zero and increasing.
Note that with default settings of the series, a divergence will be detected seldom, and because of that the GDM will be very high. Lastly, the first option is to not look at the slower series at all and trigger a divergence when the waves are getting weaker (technically there is no comparison and thus no divergence).