Python SDK ResultMessage's message.usage['input_tokens'] isn't correct

I am trying to analyze token in and out for Claude Code Python SDK.
For my task, after completion, I looked at the ResultMessage,
usage['input_tokens'] is 69
usage['output_tokens'] is 18467

The input_tokens here is really off
and output_tokens seem to be accumulated correctly.

I looked at cache_creation_input_tokens and cache_read_input_tokens stored in usage dictionary.
They don't seem to represent cumulative input_tokens.

I used this prompt for my coding task

https://github.com/RooCodeInc/Roo-Code-Evals/blob/main/prompts/python.md

and had cwd pointed to this

https://github.com/RooCodeInc/Roo-Code-Evals/tree/main/python/pov