Products with different VAT in the basket and apply discount code with a value without VAT

[CUBE-IN]

What is the calculation mechanism in Prestashop when there are products with different VAT in the basket and a discount code with a value without VAT is used?

EXAMPLE
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product 1 - VAT 0% - price 668,7 without VAT - price 668,7 with VAT
product 2 - VAT 21% - price 137,1 without VAT - price 165,89 with VAT
total - price 805,8 without VAT - price 834,59 with VAT
It's OK
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now i apply discount code for 772 without VAT !!!
total - price 33,80 without VAT - price 35,01 with VAT - so the VAT is 1,21
How is it possible? How was that count?

 

And how do I count correctly, if I don't know what product I will apply for the discount?
EXAMPLE:
I have one product in my cart for 100 with 0% VAT and the other for 100 with 10% VAT. So a total of 210 with VAT. I will apply the voucher for a discount of 100 without VAT. If the voucher is redeemed for the first product, the final price will be 110. If redeemed for the second product, the final price will be 100. So how should it be applied correctly?

Edited March 1, 2021 by CUBE-IN (see edit history)

[CUBE-IN]

No one solve this essential problem?