Sounds about right I would think, if I remember correctly it was only the pre unit construction engines that had seperate oil in the gearbox and engine, but you had best check online to make sure.
Found this and it might help.
1> Run the engine for about one minute, and shut down.
2> Remove the dipstick and drain the oil from the oil "tank" at the drain plug located below ignition cover (left side). Replace the plug.
3> Remove the top two oil pump filter bolts, then the lower one and remove the oil filter cover. Service the filter and replace the cover.
4> Drain the crankcase at the drain plug cleverly located directly behind the frame rail on the right side, below the kick starter. (yes, you do detect sarcasm).
5> Fill with 1.1 qts oil, replace the dipstick, start and run for 1-2 minutes, shut down for at least 30 seconds, and check the level.
This is for an 06 YZ450F.