SimRacin40 is correct on the NS symbols.
Some do actually tell you their destination by the number because the same symbol runs that same routed destination ever time. Sometimes extras will be used when a train hasn't been filled out such as a M94 is an extra 194.
200's are Inter-modal or auto racks. 100's are mixed timed freight. 8's are usually coal trains (loaded or empty) that originate on the system,700's and 400's most likely came from a foreign road.
Then you have local symbols that vary on each division. Here on the Pokey we use J's or U's. And district work trains at least here use 9's like a 936.
And the symbol will most always tell you the direction of travel such as a 194 is an east bound,and a 195 is west. Sometimes if the crew swaps trains en-route with another train,that crew will retain their original trains symbol.
Special moves sometimes carry odd symbols also .