This is from Google's website, and it is the size of the file that is supposed to be delivered, so it might be the right one...
That said, this update has a number of different files in it than P3Droid's FRG22D. It is of course a partial patch... Where P3Droid's FRG22D appears to be a complete update...
And more importantly, this new update includes a new recovery image. I have to wonder if this new recovery image is locked similarly as the recovery image has been on the Droid2.
If you like having your Droid1 rooted, or if you ever want to root your Droid1, I'd strongly suggest waiting to hear more about this from the pros before attemping to install it.