The amount of your refund is based on your Taxable Income, Non-Refundable Tax Credits, and the amount of tax you have had withheld (taken off).
If you have a look at your Detailed Tax Summary, you can see what your Taxable Income is on Line 260, as well as how much you have in "credits" on Line 335. If Line 335 is higher than Line 260, you will be refunded all the tax you have had withheld.
If you have any Tax Payable on Line 435, you will only be refunded the portion of tax withheld which has not been applied to that.
