Setting up Sat Nav suitable for Caravan

First of of all sorry if this post is in the wrong section. Seemed most appropriate to me. 

I have obtained a Sat Nav for HGV's Motors Homes /Caravans. If you have one of these when you set them up for towing do you put the length of the combined unit into settings or just the caravan. I have read various discussions on this and perhaps the most convincing was a response from Trimble maps to one individual who state the following:-

'In regards to your query, please note that the dimensions to enter in the RV app would be for the bigger vehicle of the two (Car or Caravan)
In RV app, you Only enter the dimensions of the bigger of the two vehicles. Either the dimensions of the Car or the Trailer. Not Car+Caravan combo.'

When I first contacted the support team of the Sat Nav I purchased the agent said a combined length. However, when I sent them the above information they changed their position. Their replies I have to say are not the best and I suspect they are agents in a call centre or something similar rather than experts on their system. 

Also the settings ask for number of axles. So do you enter the caravan axles only or combined of car and caravan ? 

There is also a box to tick for a trailer. I presume the caravan is the trailer ?

The weights I suspect are easier to work out. As I am going to France I have entered  the cars Gross Train Weight as Plated as this is what is considered in France. 

thank you in advance.

Ray

PS The length I have put into settings in image are combined but sounds like I may need to change that.