before you sent me to the schoolbenches
Apologies .. not the point of my comment. The main concern is to avoid the new chums getting confused along the way.
In my view both are completely seperate
Not quite the case. The 2.4% gross data should be viewed as an actual minimum climb capability or even marginally less than that obtained. The 1.6% is the expected gross data reduced by 0.8% to provide a reasonable, real life, margin for obstacle etc., clearance calculations.
Thus, gross approximates what you expect to see on the gauges while climbing out while net is the calculated data upon which one bases the obstacle clear flight profile for preflight calculations.
The two are inextricably linked.
but it can be less at the end of the 2nd segment
Used to cause heartache in Australia where the local rule book required that the performance be maintained throughout the second segment.