On the Quebec form how does the discrepancy between line 393 and 395 arise? Where is the calculation made?

This line refers to donations & gifts entries. 

• You will find this slip in Easy Step under the Deductions & Credits tab then Payments Profile.  
• FormsView - Tslips ,Receipts, Donations

When the entries have been applied you will view an amount on line 393 & 395 of your TP1.

Please review this link to assist you in understanding how your taxes are calculated https://turbotax.intuit.ca/tips/how-to-calculate-the-charitable-donation-tax-credit-5498

Example - If you donate $10,000 and you live in QC; your Federal tax credit will be $2872.00 whereas your Provincial will be $2392.00 = $5246.00. 

@ecron - please review the revised answer. Thank you

Somehow I discovered that the calculation is made in Quebec Schedule V.  There should be a link to that if one double-clicks.