No A is fixed based upon your steem power.

A could actually be this on the 4n curve.

X is your steem power
P is the percentage of your vote power you chose to allocate
V is the actual percentage of your voting power you have remaining based upon how much you've been voting.

A=4x(XxPxV)

Yet it appears that instantly allocates those vests. So once you cast the vote you've SPENT that. It is out there and won't change.

The total of all votes though can change which will decrease how much power A actually has.