Yep it is the symbol to tell you that it did not record all of the program that was reserved, it can happen if there is a power interruption to your hummy, such as a power cut or maybe if there was an OTA update while the box was recording, which usually results in the box rebooting itself, although thinking about it i'm not sure if an OTA update will proceed if the box is recording, what time did it happen on the 20th?.