There is a progression of leaf blade numbers throughout the plant's life.
When very young, it goes 1-3-5-7-9-up to 13 (most I've seen personally).
When vegging and mature, in good health, the plant will show the greatest number of leaf blades that its strain can produce. Some strains make only 3, tops!
When flowering, which is the end of the plant's life cycle, it starts to drop again. The last leaves the plant will ever produce are back to a single blade sticking out from amongst the calyxes.
Should you decide to re-veg the plant, it will shoot out long, skinny, unserrated, single-blade leaves that are usually called 'stress leaves'. As it becomes healthy again, it will go back up as if it were a seedling- 3, then 5, and so on.
A very stressed plant will show FEWER than the appropriate # of leaf blades for its strain and life stage.
Hope that helps!