Note: Although some letters may be more frequent, the letters only fit into the common features of country names.
This is a combination of several factors which makes up the most common name possible. It includes whether the most occurrences per letter are vowels or consonants (I.e. vowels only comprise 32-38 of first letters of countries). Also, even if there is a more popular letter for a certain space, if it is not the write type of letter (vowel/consonant) it cannot be accepted. The third letter was shared, but two letters both had the right amount of letters in their countries, and so were decided by which letter was in the right place of the right name length of the largest country.