Car 0632 would be the second sleeper from the dining car. The numbers start at the dining car and go outward. Depending on the orientation of the Zephyr, it will either be at the very front or very back of the train.
There is no 0630 car on the Zephyr (well, there wasn't recently). 0631 is the first car after the dining car, and 0632 is the second car after the dining car. For the coaches, either 0610 or 0611 (not sure which) is closest to the diner/lounge, then 0611, 0612, 13, etc.
Also, the Empire Builder sleepers are 0730, 0731, and 2730 (replace 7 with 8 for the eastbound counterparts). For example, a full consist on the Empire Builder would have line numbers: 0710 (crew dorm to Seattle), 0731 (sleeper to SEA), 0730 (sleeper to SEA), dining car, 0711 (coach to SEA), 0712 (coach to SEA), sightseer lounge, 2714 (coach to Portland), 2715 (coach to PDX), 2730 (sleeper to PDX), 0709 (coach to St. Paul).
Also, for the Texas Eagle, if the car continues on to Los Angeles (tran 421), the number is 2130. If it terminates in San Antonio, then it is 2120. I believe the transition sleeper/dorm car is number 2119.
The Sunset Limited has a weird numbering system for coaches. The first coach behind the lounge is 0213, and the second coach is 0212 (eastbound, it would be 0113 and 0112 westbound). West of San Antonio, there is also coach 2215/2115 for the Texas Eagle through-car.
That said, it should also be pointed out that often crewmembers "forget" to change the line number, so it may have a number completely unrelated to what it is supposed to be.