Please excuse my ignorance but what is a 532 Sleeper?
Cars are assigned "car line" numbers describing the train, placement in that train's consist and, for sleepers, room inventory. The first 2 digits are the train number (leading zeros often not shown), the second, the car line.
So train 5, car 32.
Standard sleepers on most Superliner trains are in the 3x car line. The exception is the Capitol Limited, where they are in the 0x car line, likely to avoid confusion with the train number, the eastbound being train 30.
They are generally numbered sequentially lowest to highest by consist position, the lowest being the sleeper adjacent to the diner.
The lowest sleeper car line on the train will be only sleeper if a given departure has just one sleeper. We have been referring to the lowest car line number for any given train as the "base" sleeper, since if that one was removed there would be no sleepers at all.
On most Superliner trains, the lowest standard sleeper car line is the "30" car line. However, on the California Zephyr, it is the "31" car line. I think the CZ's "30" had been used as the Chicago-Denver cutoff sleeper that has not been operated in several years, but the CZ "30" car line is still reserved for it. In any case, "31" is the lowest sleeper car line used for the Zephyr.
Since over the past year, Amtrak has been cutting sleepers that they have already sold inventory in, the car line number has assumed importance that it had not had before. The car lines above the lowest, the "base", are the ones being removed. So, until the situation stabilizes, space in a non-base sleeper must be considered at risk for cancellation. Personally, I will not consider the situation stabilized until Amtrak has gone a full year without removing cars with sold space. By my reckoning, they'll have to make it to October 2023 without pulling this crap any more.
531 is a base sleeper. 532 is not. Unfortunately, it makes a different under current conditions.
Finally, the car line numbers are virtual. They do not correspond to physical cars. Any Superliner standard sleeper can run in any Superliner standard sleeper car line. Further Superliners run in a national pool.