So Riot failed basic math, good to know.
this was the closest I was able to get to the 1.8 mark ( https://gyazo.com/a11c4b64527f76e4c34023c860c76667 ) which means each individual rune is worth about roughly 1.8667 AP so why didnt you round up instead of rounding down?
Also one may ask "don't you have to much time on your hands to go figure this out?" And the clear response to that is clearly XD.