The «Log» tab is a record of everything the data processor did in this session: time, action, result. How much was saved, what failed and why. If something went wrong, this is where the investigation should start: this is where the full error text from the program or from the platform is kept, rather than its short version from the status line.
The «Result» field
Below the tabs there is the «Result» line — a short summary of the last action. It answers the question «did it work or not», while the details are in the log.
Operations from the queue
The log also contains the operations that went into the program queue: «in the program queue … operation N». That number can be used to find the operation in the program itself, on the «Queue» tab.
Contacting support
To pass a problem on to support, copy the text from here — this is usually enough to understand the cause without additional questions. If the failure is on the download program's side, its log will be useful too.
Clearing
«Clear log» starts the record from scratch. The log is not kept between sessions — once you close the data processor, the record is gone. If an error is important, copy it before closing.