DLR type=%d question

Hi,

In my testing I get a type=12 url parameter sent back.  There is no 
individual
type of 12, however if I add:

        4: message buffered
        8: smsc submit

I get 12.  Is this what is happening.  Instead of getting two Delivery 
reports, 
I am getting a single one, with both statuses?

I cannot find this in the documentation, and would appreciate an answer
if possible.

I specified a dlrmask=31 (All status')

Thanks
Jason