That report also answers my question. At the top of the climb Pooley's lead was 4'30" over the group of other favourites. At the bottom of the descent, which Cicloweb describes as "quite technical", her lead over the same group was 3'19". So 1'11" lost over a 15km descent - not good, but not disastrously bad either.
To me it seems the only comparable descents at the Giro will be the Sormano and the Foscagno. The Sormano may be made easier by the fact that where it comes in the day it may not be pushed, and even if it is they're going up the difficult side on which Pooley could conceivably give herself a head start like today. The Foscagno could be more tricky, but then the Stelvio comes right after...
I'd previously thought they were going up the easier side of the Sormano, but I'm certain now they're going up
this beastly thing - special category really. Shame it comes so early in the stage.