listing-2.21.html & listing-2.22.html

[Dexter1996777]

Hello everyone!
Could you explain me please how calculation works in listing-2.21.html?

Does a browser first calculate font-size by multiplying default font-size 16 px by 2em, then a browser calculates line-height on the basis of calculated font size?

One more question, please.
In listing-2.22.html, line-height and font-size are calculated on the basis of default font-size (16px)?
As for line-height: 2em, em relates to the ancestor's () font-size (16px)?

Thank you!