Do you get your royalties as a one-off payment, or you are paid per sale of each publication on an ongoing basis?
Royalties from books purchased build up in your account until you meet Amazon's payment threshold.
Amazon's payment thresholds are here - but seem to be about $100 USD or similar equivalent. https://kdp.amazon.com/help?topicId=A3E24YJK5O82TD
Also, you get paid 60 days after the month where you exceed the threshold.
And you must meet the threshold for each country. (so if someone buys your book in another country like United Kingdom or New Zealand, you would have to pass their threshold before you received a royalty payment).
Having only sold a few books in other countries, I do not expect to ever be paid for those royalties.
With Amazon, assuming you have self-published through their Kindle Direct Publishing (KDP) program, you are paid royalties based on each book you sell, regardless of the genre. When you create your KDP account, you will have access to a portal where you can keep track of your sales in real-time and can generate reports for different time periods. Amazon issues royalty payments once a month (assuming you have generated enough sales to meet their minimum payment requirements).