Video Streaming help. Need better understanding

I am currently in the process of creating an online video recorder for my video surveillance. I was wondering if I can record files in a specific bitrate?
Example : 1 minute of recording at 300kbps = 2.2 mb.

I am currently using : my_cam.setQuality(307200, 100); to set my video quality at 300kbps. Is that correct? With that setting, I keep getting 3mb + for a 30 second clip. Why is that? I don’t want to go any lower than 300kbps.

I have even tried my_cam.setQuality(307200, 0); and my_cam.setQuality(307200);

Does flash record in bits or bytes? I am confused. someone help please!