hmmm ...... I actually posted a reply to the above yesterday - and not sure why the post didn't make it through.
But - anyway - the dosage of 1 ounce per gallon pans out to be 2 TABLEspoon per gallon. And 'tsp' refers to teaspoon, while 'tbsp' refers to tablespoon. But just for the purpose of double-checking, it usually is best to write the words, because some people really do get the abbreviations mixed up.
Also, how quickly we use up our bottle of Azamax depends on how many orchids we have. But also - when we use Azamax, it's not like we use it every day. So how long a bottle lasts just depends on how much we need to use, and how often.