Some medication specifies to take it on an empty stomach 1 hour before or 2 hours after a meal. Shouldn't both conditions be true?

No, it does not mean that you can take it right after a meal as long as you don't eat for another two hours.

Here is how to break down those instructions:

Whatever medication it is, it is absorbed best from an empty stomach. Having food in your stomach can change the conditions in your stomach, such as acidity level or the amount of churning your stomach does. So, this particular medication works best on empty stomach conditions.

In order to give the medication these empty stomach conditions to work properly, there are two "choices" to achieve an empty stomach.

1. take the medication 1 hour before a meal. This is assuming you haven't eaten in a few hours, so your stomach is currently empty. Taking the medication one hour before eating gives it enough time to get in and get absorbed by your stomach, before food comes in after it.
2. take the medication two hours after eating. This is also assuming that you won't be eating soon after taking it. Taking it 2 hours after eating gives the food that you ate enough time to pass through your stomach and into your intestine. Then, your stomach will be empty again for the medication to enter it.

Overall, depending on how many times per day you need to take the medication, it is easiest to take the medication between meals, as long as it is TWO HOURS after you last ate, and ONE HOUR before you plan to eat again.