How to overcome the problem of floating commission or how to determine the dependence of the commission?

Question

YuMoney

I use Yandex.Forms in my work .
With this form of payment, Yandex debits the transaction fee from the recipient.
Example:
Petr uses Yandex.Money for transfers in the form, the commission is 0.5%. Peter sends 100 rubles. The recipient receives 99.5 rubles.
The task is to shift this commission to the buyer. Commissions from the documentation:

On the basis of this%, when generating a link to payment, the order amount + commission is calculated and all this is included in the payment. When paying by card - reality does not match the documentation:

Because of this, there is a problem when checking the payment amount and confirming it on WebHook.
Questions:
1. Perhaps someone has encountered a problem and knows how the commission changes when paying with a card?
2. What to do in a situation where the amount of the commission is not known in advance? From ideas to give the possibility of a small error, but the idea is so-so: because it may be required from the user more than necessary or less than necessary.
Yandex support is still redirecting to departments, and says that the commission is the one indicated in the documentation.