more fingers on the leaves means more resources are available to the plant. 3 fingers = enough to survive, 5 = average wild health, 7 = very healthy plant 9 = average RIU growers growth, means the plant is growing FAST. 11-13 fingered leaves are RARE, they usualy come from specific genetics (kyles 13 fingeres strawberry cough, 13 fingered AK-48, 11 fingered NYCDiesel) and if you can get the plant to express 11+ leaves it meants the plant is VEERY healthy.
a plant will only grow as fast as the weakest link in its "food chain". a plant needs air, water, light, nutrients and a Medium to grow in (such as soil, hydro, aero). the more fingers a plant has on its leaves, the more light the plant can absorb, and the more nutrients it can use.