The gravity doesn't matter a whole lot. Less sugar is less final yeast cells. More sugar is more final cells. If you are really worried about it add a little DME to bring the gravity up or a little water to bring the gravity down.
If the gravity is extremely low you risk bacteriological contamination. If it is extremely high you risk damaging the yeast, but you would have to really mess something up to be near a problem area.
The final cell count is roughly proportional to the amount of sugar. So if you made a 1.028 instead of a 1.035 then you will have 80% of the cells you planned for. If you made a 1.050 instead of 1.035 then you will have 42% more cells.
(Mr. Malty and Yeast Calc were developed with a set of experiments at 1.035 or 9 degrees Plato.)