ooooo what does this button do? & chair issues

[carmadbaker]

can anyone tell me what the little button under the handbrake does? its kind of an exclamation mark in a circle?
and
my chair won't go up an down tried pumping it but nothing happens, is this a common problem and wat can b dun to sort it?
thanks!

[carmadbaker]

oo right well that makes sense, yer my problem with the height adjustment is on the drivers side, at the moment i look a lil dwarf like drivin my car