Ah, I see. My mistake.
Thanky you, Blind4Basics.

Hello guys,
I think that there is a mistake in the sentence: "... and 2 letters from 'allo' ('ao') ... therefore the result is 7 (the anagram is 'lo'".
It should be: "... and 2 letters from 'allo' ('al').

Besides, I think that there is a mistake in the tests:

{"codewars", "hackerrank"}
Total letters = 18
anagram = 'acer'
letters to remove from "codewars" to get 'acer': 'odws' --> 4
letters to remove from "hackerrank" to get 'acer': 'hkrank' --> 6
So,the results should be 18-10=8 and not 10.

Thank you and Cheers,
Manel