Runes Bug ?

I got to level 11 and I unlocked custom runes. It appears it is limited to just picking keystones though but for some reason I can pick a keystone and it doesn't let me complete the page with ad carry pages? (https://imgur.com/a/jcXXk7V) As you can see, I am limited to 1 set in ap runes but when I click for ad runes it will not allow me to select any at all? What is the point of selecting the keystone then ?