Scaling 3d object on image target to 'real size'

I have an image target printed on an A4, for this example lets say the size of the image target on the paper is 20 x 20 cm. In the Vuforia target manager, i have specified the width / height as 20. In theory (to my understanding), if i want an object on the trigger to appear to be a meter wide, i would give it scale of 100.

My use case is that i want to show a 3d model of a chair at the real life size, for the sake of this example lets say its 1 meter.

If i import the model obj (not made by me) the default scale is 1. If I add that obj to the image target, it's absolutely huge. Hundreds and hundreds of times bigger than the image target (eventhough the scale is one)

How can i make it so that the model matches the width of the trigger exactly if scale is set to 1? So then i can se the scale to 5 and it would be one meter (as the image is 20 cm).

Is there something i'm missing?