Vray 3.4 Render Options for Spotlight

[JSA_SJ]

Getting a bit overloaded with the render settings for spot light. With cove lighting tubes, it's easy to set up the rectangular lights and select almost all default settings then it appears to be fine but it just doesn't seem to be right with my rendered spot light - same one chosen from Vray lighting (V3.4). It could be the settings that were incorrect:

For example, the Intensity, which unit should I use - the default scalar or the Luminance (lm)? How could I convert 5w LED spot light into lm? Is the Falloff option Linear?

How come it doesn't look normal as it's supposed to be? Why is there a missing section between the spotlight itself which isn't shown on the photo and the shadow? Please help. Thanks.

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