vmdk file in OVA template

Hi,

   I have created OVA template using vshpere web client. OVA creation deployment works fine..

   But OVA contains vmdk file with "000000" as extension. (Ex :  abc.vmdk.000000000" )

   I want to know what is this "000000" for ?

When I create OVF template instead of OVA , the vmdk file in this does not have this "0000" extension.