Bell sleeve query

[mummychacha]

I'm following a pattern to make a bell sleeve. Granny stitch. The instructions say to work in a spiral, not to join the round. I have completed round 2. If I continue working 3dc in each space my subsequent rounds are ending up the same diameter, not increasing to form the bell shape. Am I missing something here or do I need an increase somewhere? There are 19 spaces at the end of round 2. I've attached the pattern & the designer's sleeve image.

[Granny Square]

I'm picturing bell sleeves as more or less fitting the arm to the elbow, then flaring out from there, like this

So the pattern photo looks right, it appears to be at the point it just started to flare.  Your pattern copy stops where it says 'work until the sleeves are 10-11 inches'.  My arms are about 10" from armpit to elbow, so I would think that is the point something different will happen beyond that point that you copied, to make it wider (probably increasing at the underarm so not as obvious).