Currently, my Net Employment Earnings (sum of gross earnings) does not equal the sum of my T4 line 14's. It did in previously years. Should I see a discrepancy?

The Net Employment Earnings line in TurboTax when reviewing income shows the sum of the gross earnings reported by entered T4's. When I manually add the T4 totals, there is about a $20 difference between the values from my T4s (from line 14) and the total reported by TurboTax. Why is there a discrepancy when in multiple previous years these matched?