Reproduction steps:
1. Open project attached.
2. Open "Test" scene.
3. Press Play.

Expected result: Particle emits at -3,0,0 and 3,0,0
Actual result: Particle emission range is between around -7,0,0 and 7,0,0. (It might change. It depends on emission rate).

NOTE:
It only happens if "Simulation space" = World.
There is a script attached, that changes Particle system position every frame. (Now it is set to -3,0,0 and 3,0,0).
Sometimes emission is between -3,0,0 and 3,0,0. To increase range, follow those steps:
1. Change "Emit from" to Base Shell.
2. Change "Emit from" back to Base.
It is expected to be only at -3,0,0 or 3,0,0 (because particle system never appears at different position).

Reproduced on: 5.3.0f4, 5.4.2p4, 5.4.3p3, 5.5.0p1, 5.6.0a6.