I just had to deal with this for a UK version of a spot i cut.
According to their guidelines, you have to export the frame of video that contains the graphic, bring it into “paint”, and from there, zoom all the way in and measure the brightest pixels. They should be 16 high. You can not count the ones that start to gray or go less than white.
Also, your titles, or disclaimers or whatever it is on screen turns out much bigger than you actually wanted them.
So, 16 is not the font size, it is the actual measurement of the title in scan lines.