Doesn't Understand fine tuned model cost

Hi there,

I am attempting to create a new fine-tuned model based on the Davinci base model, using around 2000 characters of training data contained in the “training_data.jsonl” file, which has 500 tokens.
The cost for the fine-tuned Davinci model is $0.03 per 1000 tokens.
Based on this, I calculated that my fine-tuning job would require 500 tokens and cost $0.015.
However, upon checking my OpenAI account, I noticed that the data showed 1512 trained tokens, which cost around $0.045.
I am curious as to why the fine-tuning job required more tokens than expected.