Question about pseudoephedrine and ''yield''

[Microogata]

You will excuse me because english is not my mother language.

In ''secrets of methamphetamine'', it is said that ''The yield from 1 ,000 60 mg pseudoephedrine pills about 50 grams''
What does the term 'yield' mean here ? Does it mean that from using 60g of pseudoephedrine, 50g of methamphetamine can be produced (that would be weird honestly) or that 50g of pure pseudoephedrine can be extracted from 60g of pills (a yield of 50/60 x 100 = 83%) ?

 

[MadHatter]

No, that's the yield from extraction of pseudo from 1000 pills. You take 1000 pills that contain 60 mg each, go through the extraction method described in the book, and you get 50 grams of pure pseudephedrine.