The calculation to get obtain mg of acetaldehyde from mg of acetaldehyde ammonia trimer is as follows:
(80 / 183.25) x 3 x 44.05 = 57.7 mg of acetaldehyde
80 = mg acetaldehyde ammonia trimer
183.25 = mwt acetaldehyde trimer
44.05 = mwt acetaldehyde
3 = molecules of acetaldehyde per molecule of acetaldehyde ammonia trimer.
It is stated as approximately 50 mg because acetaldehyde has a boiling point of 20 Celsius therefore adds to the inaccuracy.