Part of the values returned by the SellerListing response group
includes values for Quantity and Allocated, as shown in the following
example.
<SellerListing>
<ExchangeId>Y01Y1679802Y5496404</ExchangeId>
<ListingId>0829W011414</ListingId>
<Title>Incredible Journey,Quad Movie Poster, 40" x 30",1963</Title>
...
<Status>Open</Status>
<Quantity>1</Quantity>
<Availability>Usually ships within 1-2 business days
</Availability>
...
</SellerListing>
This response shows that the seller has one (the value of Quantity)
of the requested items.