How many times should a process be prepaged? 0 ?

This is from a run on the prof's OSP.demo

Total num of pages swapped out = 532
  due to page faults = 391
  due to page locks set by I/O = 99
  due to prepaging = 42


and this is mine:
Total num of pages swapped out = 248
  due to page faults = 189
  due to page locks set by I/O = 59
  due to prepaging = 0


If we aren't doing prepaging.. how come the .demo swaps pages due to prepaging?