You can check your usage statistics in your Taxi account.
To do this:
Click 'Organisation' from the bottom left hand corner of your Taxi screen and select 'CDN Usage'
This page will show your monthly allowance and how much image hosting you have used.
Further down the page it gives you a break down of the current month and previous months usage.
Org owners will receive an email when they have reached 80% of their limit. They can then get in touch with their CSM to discuss this further.
Hosting Images with the Taxi CDN