With regard to sizing, they said the following:
These are sized according to the official Finnish military system, the first digit of the three numbers stands for user height (6: 160-170 cm, 7: 170-180 cm, 8 180-190 cm, 9 190-200 cm) and the following two are the width (waist) according to the European system. The waist fit is quite loose, this is the way the Finnish military originally designed the fit. The idea is that the in-built adjustable elastic band is always used to tighten the waist down for a custom fit.
and
The fabric shrinks a bit in the first wash, this has been taken into account in the sizing. Your brand new pants will thus be a tiny bit bigger and longer than they "actually are". The military has specced these for wash in 90 degrees celcius (near boiling) which usually takes off a few centimeters of length and waist circumference.
When they came, they were big to the point oversized. I was actually concerned that they may have sent the wrong size. I double checked, and they sent the size I ordered.
I washed them, twice, on the highest heat setting on my washing machine: "sanitize" wash/hot rinse. I picked extra wash/rinse so it put them through the cycle twice each time I ran the load. Thereafter, I then dried them, both times, for 1 hour 15 minutes on "high" temp.
They did shrink, quite a bit and now, more or less, fit pretty close to a Medium Regular BDU trouser. If you've worn them both (BDU and ACU) I specifically say BDU and not ACU trouser, because I have always found the BDU to be more spacious and comfortable in the crotch.