Hey there,
This is a grey area in that there isn't any particular right answer. Our approach, however, is to list the amount of it at a reasonable valuation (approaches vary). Then, in the optional essay, clearly describe the method you used to arrive at that number and bifurcate between standard bonus and stock amounts.
That way, you accurately communicate your compensation but provide the adcom to easily remove it from their calculations if they don't want to include it. Also, this provides full disclosure when it comes to application verification if (did I say if?! I meant when!) you are admitted.
Bhavik