Front shifter has three positions, but front chainring is only double. Is this a problem? My Merida Cyclocross 3 bike has a double chainring at the front. After a few weeks of being a little annoyed about the awkward shifting when going up steep hills, I realized that the front shifter and derailleur actually have three positions. This means I basically have to shift twice to properly move the chain on the front chainring. If I only shift once, the derailleur ends up in some kind of chain rattling limbo state until I shift again.

Is this normal? If not, what should I do about it?
I think it's the trimming function on STI shifter as you have a Tiagra shifter set (at least in the UK)

You can adjust the front derailleur's adjusting barrel and move the derailleur a little bit to Low, so that it wouldn't rub on the chain when it's at trim level.

Then you adjust the Low limit screw to make sure it wouldn't swing the chain off the small chainring.

Usually you can shift straight to large chainring if you swing the shifter far enough (2 clicks instead of 1)

You can read more on here: http://coachlevi.com/cycling/how-to-shift-shimano-sti-levers/