One way to explain stack-height is: a)measure the total length of the head-tube. b)measure the total length of the steerer-tube from the bottom of the crown-race seat to the top of the thread. c)subtract 'a' from 'b'.
Another way of putting it: It is the total height of all the bits that make up both the top and
the bottom parts of the headset, (not including the parts of the top-race and bottom-cup that fit into the head-tube)
a small discrepancy between these two ways of measuring, because of the very top of the locknut, where it covers the end of the steerer-tube. If you measure the head-tube and steerer-tube, instead of the headset, That extra mm. or so would be missing.
so...which of these is the proper stack-height? No idea!
Hope this makes sense.
(edit; 35mm is fairly low stack, Campag. pista was about that. Alloy strada was about 40mm?)