It says that household ammonia is 5 - 10% ammonia. I estimated 3% based on the fact that I had to use about 10x more household ammonia to do the job in an emulsion, but there was a dilution factor and density to consider so I was off by at least 2x.
The statement above about Baume only points up the fact that there are several scales for Baume apparently. One was in use in the US and the other was in use in Europe. The 28% ammonia is sometimes referred to as 880 Baume or .880 Baume in European texts.
One text says it relates to density and another text says that it does not.
I have no definitive text on this as they all seem to differ on the subject.