The T3 slip itself shows the "total" of these three boxes on it. You can rest assured that these amounts are correctly transferred to your tax return.
Box 49 is "grossed up" by 1.38 to arrive at the figure in Box 50.
Box 50 is transferred to the Schedule 4, then to Line 120 of your T1 General tax return.
Box 51 is entered on Line 425 of the Schedule 1 - Federal Tax Form.