The amount shown on Line 431 of the T2209 - Federal Foreign Tax Credits form is Non-business income tax paid to a foreign country and is usually not a calculated amount. Only if you had withholding tax in excess of 15% deducted, and deducted the excess on line 232 of the tax return as a 20(11) deduction would this amount differ from the entries you made from your T-slips.
You should submit any T-slips which you had Foreign Income and tax withheld (such as T3s or T5s) to CRA to document your deduction on Line 431. If this information did not come from a slip, provide them with the documentation for which this information was obtained.
If you did make a 20(11) deduction you would have likely have had to make a manual entry and make an override in the software to enter it. If this is the case, CRA would like an explanation and verification of your calculations.