NightwatchJS - Response from elements command with chromedriver standalone

I am receiving different results in responses when using client.elements command, comparing ChromeDriver standalone execution of the tests and while running on Selenium Server. Here is the output from selenium:

{ ELEMENT: '18' }

And here is the output from ChromeDriver:

{ ELEMENT: '0.3628625391025624-9' }

Can someone please explain why is this difference taking place in ELEMENT'S ID ?

via andddrey