Does e-grader gives more bands than a human?

Can anybody tell me that how much reliable are e-grader scores?

As I know, e-grader is designed for practice purpose. It can help find your essay flaws compared to other users, for example:

No of words: 256.0 315.596192385 81% => More content wanted.
Unique words: 142.0 176.041082164 81% => More unique words wanted.

look at this warning message:

More content wanted.

because most users give 315 words, while you only give 256 words, so the e-grader is expecting more words.

look at another warning message:

More unique words wanted.

the average unique words are 176 words, while you only have 142 words, so next time when you develop essays, you will need to pay more attention to unique words.

etc...