Hi Marco.
Just to confirm you are looking at the correct chart -- not the dropped packets one?
The link posted does not provided the full picture for setting up traffic shaping. You need to (1) first set up/define a traffic shaper or use an existing one, (2) create a new app sensor or add an entry for an existing app sensor -- the new entry will be for Google/media. Set the (reverse) traffic shaper to what you created in step (1) above, (3) apply this app sensor to your existing firewall rule for HTTP/HTTPS traffic. This information is pretty much covered in the Traffic Shaping handbook.
Because youtube uses various local content providers for video streaming, traffic shaping may not work well or not at all. Also the fgt may need to be able to perform deep or SSL packet inspection in order to determine if youtube is being accessed (via HTTPS).
