Google Translate API grossly overcounts sent characters

[Sandy Go]

Google API is trying to charge me $4k for API translation services for the last 2 months. For the life of me, I cannot find any report that would tell me exactly how many characters they think they've translated to come up with $4k. (based on $20/million, it should be around 200m characters)
However, I do have a detailed log on my server. This log file includes --FULL-- text to be translated and --FULL-- text that they've returned and additional info such as transaction ID and timestamp. That file is 23Mb (wc -c file - counts: 23,647,639 characters including new lines) The total number of request my server made was around 407,000... 
In other words, no matter how I count I come up with 10-20 times LESS characters.

Could somebody please point me to how I could reconcile this? 

[Raul Saucedo Ramirez]

You can read this oficial documentation about Cloud Translation[1]. Another option you can use is this calculator about Cloud Translation[2].

[1]https://cloud.google.com/translate/pricing

[2]https://cloud.google.com/products/calculator