Problem with voucher rules creating two separate discounts

[webmasterEZ]

We are experiencing an issue with a voucher (name obscured for privacy) that should:

not be compatible with other discount codes,

not apply to products already on sale,

but remain compatible with multipack discounts.

We created a rule to exclude specific products already discounted. This part seems to work, but the system still generates two different discounts, and we don't understand why.

Please refer to the attached image:

The first product, Zeta Colest (€19.46 × 6 packs = €116.82), is the item that should receive the voucher discount, and the resulting discount €35.05 is correct.

The second product, Entero Mirto (€9.73 × 3 = €29.19), is already on sale and should not be affected by the voucher — and indeed it isn’t.

However, the system shows €35.05 correctly between the items, but in the cart summary it displays a total discount of €41.22. Could you clarify why this mismatch occurs and how to resolve it?