Graph result Interpret

Hi Team, I am consultant in IT Company and creating report on Jmeter. I am using Jmeter 2.3.2 on windows. I did load/performance testing for a web site 'castiron.com' and now I am viewing result in form of graph and getting following result. No of Samples: 20 (got it) But I didn't get the meaning

Dynamic User Parameters

Hi, I have a page with url = http://www.example.com/index.php?id=123-DEF, where the first 3 char is number, separated by a dash, and followed by 3 English character. Without using customized input file such as {_StringFromFile(...)}, is it possible jmeter would do the calculation for me? Thanks.