Self-employed CPP premiums

Filling out tax return on Turbotax. Self-employed income (approx. $4500) entered as business income, and TurboTax shows amount owing for CPP premiums. However, there is no deduction for the yearly $3500 exemption. It appears that it is deducting a different amount, or none at all, as it shows almost $400 owing (before deduction for tax already paid). Any advice?