RJ Emery near Santa Fe, NM
In most cases the symbol reflects the direction "East or West , North or South" the train operates.
Before the NS/Conrail merger the NS trains running East had even symbols,and those running west had odd.Example: train 184 ran east,train 185 ran west.The 185 symbol is still used running west,but since the merger most train symbols here on the Pocahontas Division have changed to all kinds of odd and even.We have alot of odds running east and evens running west.It mainly effected our empty coal hoppers and loaded coal train symbols.The freights all kept the same symbols.
Hope this adds a little more information .
Collin ,operator of the " Eastern Kentucky & Ohio R.R."