xml: number of rows in openxml

I have this XML
declare @hind int
declare @xmldoc nvarchar(1000)

set @xmldoc = N' <Inventory>
<Item ProductID = "10" ProductDesc = "Aluminum Beam, Angle">
      <Trx TrxID = "11" TrxDate = "4/19/2008" />
      <Trx TrxID = "18" TrxDate = "4/27/2008" />
</Item>
<Item ProductID = "11" ProductDesc = "Steam Beam, Angle">
      <Trx TrxID = "25" TrxDate = "1/1/2008" />
      <Trx TrxID = "27" TrxDate = "2/13/2008" />
</Item>
</Inventory>'

query 1
exec sp_xml_preparedocument @hind output, @xmldoc
select *
from openxml (@hind,'Inventory/Item',2)
with
      (
            ProductID int '@ProductID',
            TrxID int './Item/@Trx',
            TrxDate varchar(10) './Item/@TrxDate'
      )
exec sp_xml_removedocument @hind
only show productid 10 and 11

query 2
exec sp_xml_preparedocument @hind output, @xmldoc
select *
from openxml (@hind,'Inventory/Item',2)
with
      (
            ProductID int '@ProductID',
            TrxID int './Item/@Trx',
            TrxDate varchar(10) './Item/@TrxDate'
      )
exec sp_xml_removedocument @hind
only show productid 10 and 11 (2 rows)

query 2
exec sp_xml_preparedocument @hind output, @xmldoc
select *
from openxml (@hind,'Inventory/Item/Trx',1)
with
      (
            ProductID int '../@ProductID',
            TrxID int,
            TrxDate varchar(10)
      )
exec sp_xml_removedocument @hind

show productid 10 and 11 two times (4 rows)

what is the difference? 2 and 4 rows?