First time with taxes. I'm confused?

Ok I'm a student working this temporary summer job and i won't make more that about 2,000 or 2,500. So on the W-4 my supervisor said I didn't claim enough allowances and the government is going to tax the hell out of my income. How many allowances can a single girl with no dependents have? Is there anyway I can claim exemption? I've done it before but that was when i was 16 and I made well over the $800 cap they put on....