I just did a small test for preprocessing run in one organisation, having chosen the detailed log.
And my log looks similar to yours.
But my spool file looks much different, I have actually 93 pages for 2064 orders in the selection
you said that your items have not got the deletion indicator, hence I suggest to run it again in test mode. Just to see if the same number of documents is selected, and to check if you can get the detailed log.