Had my 06 STi PPP for 1 month now. The big coolant resevoir on the front right of the engine bay was on the minimum mark when I collected the car so I topped it up. Now, three weeks later I checked the levels after cleanign the car. It was back to minimum.
The little coolant resevoir in the middle of the engine bay is full.

Is this normal as car does not appear to be leaking.

 

I would top it up again to max when cold.
My 03sti took Two top-ups after a coolant change to settle down to between min and max when cold, its been fine for months now.