There is an option to include a time stamp in a document that signifies who downloaded a document, when the page was created and importantly what domain (e.g. sandbox, test or production). The option is managed by document category editors with the "PDF User/Time Stamp" setting (see below)
The information can be shown as a watermark or in the header of the document (see examples below).
Since each page is created on demand with this custom time stamp, it is possible for the time stamp to be slightly different from page to page. This is especially true for longer documents and would easily affect the 'seconds' value.
Also, please note that if you issued a Controlled Copy, the time stamp logged in the controlled copy table signifying the time/date of the 'request' may be different from the time stamp on each generated page.