As per JMeter Glossary
Standard Deviation is a measure of the variability of a data set. This is a standard statistical measure. See, for example: Standard Deviation entry at Wikipedia. JMeter calculates the population standard deviation (e.g. STDEVP function in spreadsheets), not the sample standard deviation (e.g. STDEV).
So basically 10 is the result of applying the standard deviation formula to all response times.
With regards to your approach - it doesn't tell the full story, you don't actually create high load as I can only see 2 virtual users. Normally people are interested in answers to 2 questions:
- Will the application handle the anticipated load providing reasonable response times (so called load testing). In this case you need to mimic real-life API usage with JMeter and simulate the number of concurrent users (or applications) accessing your API.
- When (and why) it will gonna break (Stress Testing). In this case you should start with point 1 and gradually increase the load until response time starts exceeding acceptable value or errors start occurring (whatever comes the first)
Check out Why ‘Normal’ Load Testing Isn’t Enough article to learn more about approaches to testing your API.
Also be aware that you can generate HTML Reporting Dashboard which provides way more statistical information and interactive charts so you will be able to analyze your test results more easily than using any JMeter Listener.