Panel #1
Actually, speaking of books, you have one about numbers that could explain this whole octal/decimal thing! It's really a thrilling read, although somehow you've never been able to convince any of your closest friends of this fact.
Panel #2
Here we are! "Fancy Mathematics: A History." This book has got all sorts of fascinating stories, but at present you're just interested in the history of numeric representation.

Today everypony uses MAREABIAN NUMERALS, but the earliest recorded system was QUARTAL, that is, base 4. Ponies would count 1, 2, 3, 10, 11, 12, 13, 20, and so on, adding to the next highest column every time they hit what one nowadays calls four. This was based on ponies having four hooves, but as time went on it became analogously linked to other quadripartite distinctions, in particular the four breeds of ponies: EARTH ponies, PEGASI, UNICORNS, and ALICORNS.

Understandably, the earth ponies came to resent being associated with the lowest possible of numbers. Nopony wanted to risk dissent among breeds, lest they incur another GREAT BLIZZARD of the kind that covered Equestria before the earth ponies, pegasus ponies, and unicorn ponies joined together, and so the quartal system was scrapped and, after a brief flirtation with OCTAL numbering, replaced with the DECIMAL one everypony still uses. Your octal fetch modus is admittedly something of a pretentious throwback to that brief octal period, in the hope that somepony will notice your fetch modus, discern the reason for its number system, and comment on how obviously brilliant and well-cultured you are. practice, not even Colgate has made that connection, but a girl can dream.