How could 45 milligrams of a substance equal 4,500 micrograms?
This is a typo.  In the text he states:


  ... only 0.120 milligrams (120 micrograms) of MK-4 ...


So, he knows the correct conversion.

Then:


  ... the "same" product is almost 40 times more potent in one country
  ...


40 times 120 micrograms is 4800 micrograms -- which is close to 4500.

So, that suggests that the (4,500 micrograms) in the table is correct and that the 45 milligrams is a typo. 

It should read 4.5 milligrams.