Amazon how to get TotalNew

Good morning, I'm trying to request a list of products of a specific Node with Amazon API. I have already an AWS ID.

I search for these responseGroup:

Large

Variations

OfferFull

But When I get the response OfferSummary is always:

 OfferSummary => object(SimpleXMLElement) {
        TotalNew => '0'
        TotalUsed => '0'
        TotalCollectible => '0'
        TotalRefurbished => '0'
    }

Why?

How can I get the totalNumber of Items?

I have also tried with these responseGroup:

Medium
OfferSummary

I don't have xml request because I'm using a plugin to generate request.

I get all the others value but TotalNew or TotalUsed is always 0.

Can someone help me?