きゅう with the smaller ゆ is akin to saying kyuu (the word we're looking for)
きゆう with the bigger ゆ is akin to saying kiyuu, and isn't what we're looking for. Smaller letters modify the letter before them (though not all letters as you learn more you'll figure it out, it's mostly the i letters though with some exceptions.
Note the size of the ゆ; it isn't the normal "Yu" kana, but the small ゅ that modifies the sound that comes before it
きゆう says "KiYuu" which makes three syllables and would be incorrect
きゅう is written and pronounced "Kyuu" only two syllables and means "nine"
Type "Kyu" instead of "Ki yu"