I am a full time student, 20 years old. My parents claimed me. Why does the federal amount I owe on less than 12,000 income, go up with information about their return?

If you have more than $2,200 of unearned income on your return, that income gets taxed at your parent's rate.    You most likely have a Form 8615 included in your return.  

Purpose of Form

 For children under age 18 and certain older children described in this link (When does the Kiddie Tax kick in), unearned income over $2,200 is taxed at the parent's rate if the parent's rate is higher than the child's.  If the child's unearned income is more than $2,200, use Form 8615 to figure the child's tax.

Unearned Income 

For Form 8615, “unearned income” includes all taxable income other than earned income as defined later. Unearned income includes taxable interest, ordinary dividends, capital gains (including capital gain distributions), rents, royalties, etc. It also includes taxable social security benefits, pension, and annuity income, taxable scholarship and fellowship grants not reported on Form W-2, unemployment compensation, alimony, and income (other than earned income) received as the beneficiary of a trust.