Awesome library, need help with acceleration emitter.

[kylin17]

I want my particles emitter emission from bottom to top direction, and I found example activity "Emit with Gravity" similarly, so I changed the code below to made it emission with 270 angle:

new ParticleSystem(this, 100, R.drawable.star_pink, 3000)
		.setAcceleration(0.00013f, 270)
		.setSpeedByComponentsRange(0f, 0f, 0.05f, 0.1f)
		.setFadeOut(200, new AccelerateInterpolator())
		.emitWithGravity(arg0, Gravity.TOP, 30);

But the result is the particles first little down then emission from bottom to top. How should I do to avoid that little down?