Just remember UP, DOWN, ALL AROUND.
Fertilizers can be high numbers or low, these represent a % of nutrients are in that bag per pound. If you purchased a 10-10-10 10 bag of fertilizer, 1 pound (or 10%) would be Nitrogen, 1 pound would be phosphorus, and 1 pound would be potassium. The remaining 70% is simply filler, or inert ingredients, which are there mostly to help disperse the chemicals. High fertilizer numbers are more concentrated then low. Commercially produced fertilizers tend to be higher numbers then natural derived fertilizer like manure or compost. Be aware high number fertilizers CAN burn your plants faster/more then a low number fertilizer.