All-access is counted when the bytes leave the server. They are applied when you disconnect from the server. All of the times shown in your access history are the ending times of your sessions.
We have two independent processes that calculate the amount accessed. They are checked against each other to make sure the accounting of bytes is accurate. Proper access accounting is a very high priority for Giganews.
Most binary attachments posted to Usenet are 'un-encoded' by the posting software, which converts the binary file into a text format for transfer over the Internet. This can add as much as 40% to the size of the file being attached. Large attachments are then split into multiple smaller parts, before being uploaded to the posting server. The file is accessed by your newsreader, the multiple parts are combined, as necessary, and then the file is 'un-decoded', 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 attachment 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 file size to access amount.
Platinum and Diamond unlimited Usenet memberships are not subject to access limits.
If you need any further assistance, please contact our 24/7 Customer Success Team, who would be glad to assist.