The numbers entered under Net Capital Loss Carrybacks didn't affect total refund. I also don't see it in the final tax summary. How is it calculated and submitted to CRA?

Your Net Capital Loss CarryBack amounts will not affect this year's tax return.

As long as you have completed the "Net Capital Loss Carrybacks" page, your amounts will be transmitted to CRA and they will make the necessary adjustments and reassess any years you have applied these losses towards. 

When you do the Review using TurboTax Online, in the Tax Savings Opportunities section, click Explore next to "Any losses not applied to the three preceding years can be carried forward and applied against future years", and then "Applies to me". You can then continue to the page "Net Capital Loss Carrybacks". Here you can see how much of a Net Capital Loss you have incurred and make your choice to carry it back, or forward.