The formula below taken from the curriculum has X in the numerator, which is explained to represent ‘strike’ as in other formulae. The denominator has ‘strike price’ written out. Are these two different things? If not, why isn’t the notation consistent?
For settlement amount, yes “X” and “Strike Price” are the same thing here. Possibly this odd framing happened due to them cutting the notional variance formula from an earlier part and plugging it into a later part of the text.
Cheers - good luck - you got this 
Truth be told, sometimes the CFAI text are poorly worded and confuse more. Some of the topic areas are made to look excessively difficult that otherwise could have been elucidated in a much simpler manner. My two cents
Totally agree - the derivatives section is hard enough already! No need to complicate it further with wording😂