It should feel like fine sand. A bit finer than sand from Bondi beach but not as fine as flour.
Or grind to a fine sand and then run your extraction - if its too fine you wont get your approx 25 mL in 25 secs so make it courser - its its too course it will come out too fast.
I have a Euro grinder, same construction but yours is far better looking. Once you get the grind right you just leave it at that I find.
PS. yours has a nice Hario label whereas other Hario grinders like here http://coffeesnobs.com.au/YaBB.pl?num=1231888328/3#3
dont have the label. What I wonder? Looking on the internet I can see one like yours.