Excellent observation @crispi1962 !
Not sure if that is the only thing, but you’re right: the plane is set to emit 1000 particles in 200 frames, starting from frame 1. So on frame 0 no particles will have been emitted yet. And indeed, we can see all zero particles (meaning none).
On frame 1 there will be 5 particles, on frame two, 5 new ones will be emitted, and so on.
As their lifetime is set to 50 frames, there will never be more than 250 particles in the scene.
