U probably want to keep the diameter of the support as thick as possible and avoid using the smallest ones if possible, or if not less of it. No knowledge but pure guess work on my part. For myself, since i always have to extend all of them, it seems easier to lengthen the smallest one first cos as i release the next one the clip for the smaller one gets further away and a bit awkward to reach. just me.
my own perference: I extend the thickest part of the tripod 1st and descending to the lower thinner ones.
No reasons but I have been taught this way back in Film school as logic serves, you need the stronger columns to support your camera when not in full extend. so if you extend the lowest thinnest legs 1st and you only need your tripod to be in 1/2 height, it may not be so sturdy, esp in wind conditions or when you have to rest your weight on your camera/ tripod when shooting something in a leaning forward position.
i juz found out that while holding a heavy setup (like F100 with MB-15 + AF 80-200ED) and you WANT to have the length max-ed out, i'd start with lowering the smallest legs first then the middle. that way i dun hafta bend down and release the smaller ones after releasing the middle ones and then straighten my back again. true 190 is kinda short eh? i needa raise the center column as well, making it less stable.