I haven’t touched AB in a long time, but if I remember correctly it is the percentage of your particle life, not your total frame count.
So if you have a particle spawned at frame 0 with a delete operator set to delete them at frame 60, then 100 in the AFC equals 60 frames of particle life, and 50 in the AFC would equal 50% of the particles life so 30 frames. The total frame count of your animation doesn’t matter.
I’ve been told you should always have a delete operator with afterburn or else the AFC’s won’t work properly because of what I stated above.
Just trying to clear things up in case there were some misunderstandings.
(if I’m wrong then please correct me)