All Usenet access is counted in bytes, applied when you disconnect from the server. All of the times shown in your Control Panel are the ending times of your sessions.
We have two independent processes that calculate access amounts. They are checked against each other to make sure the accounting of bytes is accurate. Proper accounting is a very high priority for Giganews.
Most posts on Usenet are 'unencoded' by the posting software, which converts the posts into a text format for transfer over the Internet. This can add as much as 40% to the size of the post. Large posts are then split into multiple smaller parts, before being uploaded to the posting server. The post is accessed by your newsreader, the multiple parts are combined as necessary, and then the post is 'undecoded', before being saved to your hard drive. This will account for the difference in the bytes accessed and the bytes saved to your hard drive.
The yEnc encoding method, which is now fairly ubiquitous on Usenet, compresses the post into a 7-bit format. Most recent newsreaders have yEnc decoding built-in. With built-in yEnc decoding, you should see much better ratios of post size to access amount.
If you need any further assistance, please contact our 24/7 Customer Success Team, who would be glad to assist.