Box 21 of my financial institution’s T3 has the capital gains amount indicated for the relevant securities.

There are 2 box 21’s in turbo tax, one for capital gains and one for amount of those capital gains that are foreign.

How do you confirm what percentage of box 21 (capital gains) on your financial institution’s T3 is foreign?

Is this based on wether the Stock/ETF  holds companies outside of Canada? Or I have also seen references to this being identified as a footnote on the T3?

Appreciate any help or clarification on this point.