10 10 10 on a bag of fertilizer tells you the percentage of nitrogen, phosphorus and potassium in the mix. Bloom booster fertilizer will typically have a higher level of phosphorus. The bag may also say "no urea" which is a source of nitrogen. There is a school of thought that thinks nitrogen derived from urea is not effective on epiphites because it cannot interact with soil. I don't buy that but then that is just me. The bag may also list minor elements like magnesium, boron, ect., and tell you if some of the nitrogen is slow release. There is lots of good information on a bag of fertilizer.
Jim
