long The total number of bytes read by the asynchronous file read request.
Returns the total number of bytes read by all the ReadCommand operations the asynchronous file read request.
This may not be equal to the sum of all the requested ReadCommand.Size fields in the case of a ReadStatus.Failed error or a ReadStatus.Truncated status. In these cases the AsyncReadManager will have updated the Size fields with the actual number of bytes read.
A truncated read occurs when the ReadCommand describing the read operation specifies a ReadCommand.Size and ReadCommand.Offset that extends past the end of the target file.