How to increase performance in EngageOne Server when File Partition Number is small

Partition size determines how many records are run for each file.

For example, if using an XML file with 1000 start of publications and set the file partition number to 5 it will take 5 Minutes and 14 seconds to process all the entries resulting in 200 PDF files.  If I take the same file an set the file partition number to 1001 it will take 19 seconds and will only produce one file.
Environment Details
Software Affected: EngageOne Server
Product Feature: Batch (Non-Accumulated)
UPDATED:  November 3, 2017