Hikmarket marketplace fees calculation for vendor with coupon

Hello,

I don't understand the calculation of marketplace fees in case of use of a coupon in an order.

I have a product with a normal price of 649€ with tax, and 10% marketplace fees (64,90€), for a net value for vendor of 584,10€.
The coupon is 50€ HT (60€ with tax), with option "Yes" to "discount applied to vendor" (see attached for coupon settings)

The net price of the product is correct (589€) but if we look at the order price detail, it seems that there is miscalculation on the coupon value, with 60 w/o tax + 10 of tax (see attachment), so a total reduction of 70.
The net value for vendor is 514,10 in the order.

In Stripe, we received 69,70 as fees, and the vendor received 519,30.

First, I would like that the fees to be calculated on the net price, what settings should I use to achieve that ?
Second, it seems the info transmitted to Stripe is wrong ?

Thanks for your help,

Marina