FPS/Network Display Box ("F" key in-game)

The FPS/Network Display box shows you three values:

FPS (graphical frame rate in Frames Per Second, or FPS)
L (Latency, or data transmission delay between your system and the iRacing server)
Q (Quality of the connection to the iRacing server)
S (Sevice, shownig the state of Synchronization between your computer and iRacing)

The "FPS" indication at the top of the display is a numerical value that represents your frame rate in Frames Per Second (FPS), which is a reflection of your graphical performance.

The "L" portion is a bargraph that represents your latency of your connection, or the time delay for data transmitted between your PC and the iRacing servers.  This bar can vary in length and in color -- a shorter bar length or a green bar indicates a low latency or delay, and if this bar turns red that indicates that your latency is reaching an unacceptable acceptable level.  When you see a red bar here, this is an indication that the latency has dropped to an acceptable level, which may result in a disconnection from the iRacing server.

The "Q" portion is a bargraph that represents your connection quality, and this bar can display varying colors -- a green bar is good, yellow or orange means less than ideal connection quality, and it will turn red if your quality is dropping below an acceptable level.  When you see a red bar here, this is an indication that your connection may drop and you may be disconnected from the iRacing server.

The "S" portion shows the service/sychronization state, or the "skew" of your connection to the iRacing servers.  As with the "Q" bar, a green bar is good, yellow or orange means less than ideal synchronization with the iRacing service, and it will turn red if your synchronization is dropping below an acceptable level.  When you see a red bar here, this is an indication that your connection may drop and you may be disconnected from the iRacing server.