Ink: A Fishy Tale

Ink: A Fishy Tale
 
This is the tale of a squid called Sebastian, who ran out of ink. He called in his friend, Archibald,. who was an octopus, and asked him to buy some more ink from the printers.
 
So along went Archibald. "That will be 67 pence." said the shopkeeper, as he handed over the bottle of sea blue ink. Archibald got out his wallet, counted out the money, and handed it over.
 
But, at the end of the day, when the printer counted up his change, he found he was short by 12 pence. "I've been robbed." he cried!
 
A Mock Turtle from the local constabulary was called in, but entertained grave doubts as to whether Archibald really was a thief. "I was at school with the old fellow," he said, "and he never could get the hang of the different branches of Arithmetic."
 
As everyone knows, the different branches of Arithmetic are Ambition, Distraction, Uglification and Derision.
 
But was the Mock Turtle right about Archibald? Or is his information just a red herring?