Some powders show more pressure excursions then others, and I would think this may be the reason the loads were listed the way they were.
Let's say that for a given round, the Saami pressure is 30kpsi, powder A produces an average pressure of 29kpsi +/-1kpsi, so is listed up to 29 kspsi. Powder B produces an average pressure of 25kpsi, +/-5kpsi, so is listed up to 25 kpsi.
I'm not positive that this is the issue with Lil gun, but I'm sure there is a reason it is listed the way it is. I've heard pressures rise quite fast when using max loads in Lil gun, so don't just assume you can keep adding powder guessing at what pressures you are reaching.