Do not expect any serious calculation on that part of the test.
The 10/14 is going to be enough, the point is to make the calculation quickly and rightly for the first time so you don't waste your own precious seconds.
That's what all FEAST is about: be quick and right. If you screw up something and you can't correct it just go on and concentrate on the new things instead worrying about the (previous) screwed ones.