As I mentioned before, note 1 important point.
If a student has applied to BOTH RPI and Union for a BS/MD programs, then AMC will invite for an interview ONLY after they know the decision from both RPI and Union (one way or other). Also to get the supplemental app initiation will defer considerably. Because of these points, some students may get quick responses and for some it may take a very long time and mean time both students and parents get worried. So be patient. Let me drive the point with the example @narkor has provided above.
In @narkor D case since her app is so strong (she got admitted in both programs) both RPI and Union forwarded and AMC asked to submit supplemental app by 11/30 & 12/10 and got interview invitation by 1/4.
In my D case, though she was asked to submit supplement app by AMC for Union on 12/5, there is no further word from any one (RPI, Union and AMC) where as meantime folks were getting not only invite to submit supplement from RPI but even interview dates. Apparently, AMC was told that RPI has plans to forward my D app to AMC but in the bottom of the list and hence AMC holding of their decision on Union/AMC because the interview is the same day for RPI/union candidates if they are selected. So finally RPI/AMC asked my D to apply on 1/12 and submitted by 1/22 and got rejection for both RPI and Union by 2/2.
So the gist is to get supplemental for RPI/AMC may take all the way from 11/30 (@narkor D) to 1/12 (my D) (44 days is eternal when most of the other schools gives invite/rejection on the same day). Meantime because of RPI took more time, the Union decision took its own time (submitted on 12/15 and only 2/2 got the rejection - 48 days).
If you have applied only to RPI or Union you will get to know the results much faster. Albany/AMC is treated separately and has no impact to what I am trying to say here.