Numerology: Multiple Digit Numbers vs. Single Digit Numbers

Question: I understand that there are various ways of calculating the destiny number. For instance, for the date July 26, 1985, you could add as follows: 7 + 26 + 1985 = 2018 = 11 = 2 or 7 + 2 + 6 + 1 + 9 + 8 +