How many allowances should I have on W-4 as first job out of college, single, no children, etc.

How many W-4 withholdings should I put for my first job?
I am single, independent, job is in MA, etc.

This is my first job ever, and I am wondering what difference it would make if I put 0 or 10 for allowance. The IRS calculator I used online recommends I put 10 for allowance, but what does that really mean?

Thank you!