Please refer to the following URL for details.
How to avoid a shadow due to an inner cover (Indoor PTZ camera) | i-PRO Products

There are two ways to limit the tilt angle of the camera.
(1) Limit tilt angle
From [Setup] → [PTZ] → [Cam.Function], set angle limit of [Tilt Angle].
The angle that can be set differs depending on the model.

 (2) use [Pan/tilt range setting]
From [Setup] → [PTZ] → [Position] → [Pan/tilt range setting], set [Pan/tilt range setting] to "On" and adjust the angle of view with the control pad/buttons to set the [Left end]/ [Right end]/ [Top end]/ [Bottom end].
Adjust the angle of view and click [Set] button to display the angle of the set position.