While it can be frustrating, it’s common for the Canada Revenue Agency (CRA) to make a tax return assessment that is different from yours.
The reasons for these discrepancies may vary and can range from very simple (typo or data entry error, forgotten slip, receipt, amount, etc) to complex (carry-forward amounts not included, accounting errors, etc).
In most cases, the CRA will explain how they calculated your tax refund or balance owing, and you can find this information on your Notice of Assessment (NOA), under the heading Explanation of changes and other important information. Compare the line numbers on your NOA and their corresponding values with those entered into TurboTax.
If you're eligible for the disability tax credit, you'll have disability amount claim on line 31600. This TurboTax Canada FAQ has information on how to get a PDF copy of your tax return in TurboTax Online: How do I print a copy of my tax return in TurboTax?