the roman numerals are all good man its the elements. the "N" in "Na" is adding 90 onto the numeral rule, for rule 18 you can use multiple two letter elements j

the roman numerals are all good man its the elements. the "N" in "Na" is adding 90 onto the numeral rule, for rule 18 you can use multiple two letter elements just try and find ones that don't contain roman numerals and you'll be fine