How should the unit be tilted during installation, and why?

The unit should be installed with a slight tilt towards the outside of approximately 3° (about 10–15mm, or a 1/4 bubble with a level) to allow condensed water to drain properly. Improper tilting could lead to water buildup inside the unit. The housing should also slope down towards the rear by about 5mm for the same reason. (Page 15)