It is an explanation of what the term "video bitrate" means (i.e. the speed of video encoding in kilobits per second).
Last edit: 11:48, 4 September 2011
Yes, I often run into the same ambiguity problems that you mention, but this specific English message is particularly badly written. Perhaps someone should rewrite it (Siebrand?).
Anyway, the message name is "videoBitrate-help", so surely it should be an explanation of what it generally is. What I translated is: "'bitrate' means the encoding speed of the video (in kb/s)."
Please suggest alternative text. Busy today until I get to my hotel room later today.