Calculate power consumption of series 500 modules

Currently it's not possible to add the power consumption of Series 500 modules like we do it with Eurorack systems.
That should be improved. The goal is, that it should be possible to calculate the power requirements of all modules that are added to an enclosing/rack so it would be easy to verify that a power supply is sufficient.
We missed to collect power data for Series 500 modules so that must be added at first.
I am not so deep into electronics so I need some help:

I have read in the 500 Module Series Spec that a bus connector delivers +16, -16 and +48V.

That matches with the API lunchbox that has three LEDs, labeled with +16, -16 and +48V.

I guess these basic assumptions are correct:

• Every 500 Series compatible enclosing has a power supply that delivers +16V, -16V and +48V.
• To calculate the power consumption of the system, all three values of all modules must be summed separately.

But I am not quite sure how that matches with the spec of e.g. the API 512c module.

512C has a switch for 48v phantom power but the spec only says:
Power Consumption: ±12/18 Volts/DC, @40 ma.

That mismatches with the 16V spec.
1. How should user enter this data into the database?
2. Can those values be converted to 16V?
3. Do we need additional fields in the database?