Omniscient Dumbledore and the time paradox

[weeoo0]

No: HPFGUIDX 54987

First off, I apologize if this  posts twice, I have been having some
difficulties with my email logging out.

Well, I have been re-reading PoA again, paying special
attention to the ending, trying to resolve in my mind
the "time paradox" by thinking about it more linearly,
as was suggested when this topic was dicussed a few
weeks ago.  
However, one point of interest which stuck out in my
mind was that when Dumbledore is talking with HH right
before they use the time turner he says 
"If all goes well, you will be able to save more than
one innocent life tonight" (PB, pg. 288 can ed.)
now, thinking along a linear timeline, by this point
in the timeline, HH2 would have already rescued
Buckbeak (the other innocent life they were to
save)and would have done so without being seen. 
Dumbledore  bought HH a little extra time when they
are first rescuing Buckbeak by reminding Macnair he
has to sign the execution notice, whether he does this
by coincidence, or by possibly having seen Harry
struggling with buckbeak, or maybe he just *knows*
So i am wondering, how omniscent is Dumbledore?
He tells HH they can save another innocent life
referring to buckbeak, when, using a linear timeline,
buckbeak has already been saved.
I realize this has already been discussed ad nauseum
on this list, but it's been bugging me.
thought?

Weeoo0