Your tax return is the form you send to the government that shows your income and calculates your tax. The money the government sends back to you is your refund.
The amount of your refund has nothing to do with how long you worked. Your tax return calculates your total tax for the year. The tax that you had withheld from your pay during the year is applied to the total tax on your tax return. If the amount you had withheld is more than your total tax, you get a refund of the excess. So the amount of your refund depends on how much your total tax is, and how much you had withheld.
Your tax refund is not at all proportional to your income. It depends on your tax liability and the amount of tax withheld.
The tax withholding tables are designed so that you pay enough tax as you earn so that your refund or your tax due is as close to 0 as possible. In fact, if you have a large refund at tax time, this means that too much has been withheld from your paychecks during the year.