[Unity] What is the unit of the object length value? And how does it scale?

Hi,

I am the latest Vuforia Unity SDK together with the latest Unity Editor on HoloLens. Since I am targeting a rather large object I've printed the object scanning target in DIN A0 size, which is 841mm x 1189mm. Now the default value in the object target prefab in the "Target length" field is 142.5. I assume these are also mm units. On a DIN A0 scale the value I enter here should be 570 I guess (see picture).

But entering 570 there, makes the object scale up to (570, 570, 570), which in default Unity units is huge. Like 570m x 570m x 570m.

The object is then tracked by obsviously since Unity (or Vuforia?) thinks its 570m large, it gets positioned totally wrong. E.g. I stand exactly in front of the object but my augmentations get positioned really far away.

Well, I hope you get the idea of what confuses me. 

Put simple:

How to use the object length field to specify the object size?

Cheers