Interesting thought. He's been using the number 77 for several years. However, that theory only holds true if he was using the English alphabet. The Bulgarian Cyrillic alphabet, which is used in Bulgaria, is completely different.-
Аа, Бб, Вв, Гг, Дд, Ее, Жж, Зз, Ии, Йй, Кк, Лл, Мм, Нн, Оо, Пп...