French to English Bus/Financial Business/Commerce (general) Incorporation of a company (in Tunisia)

Hello.

I am proofreading a translation for someone.
Context: notes on an Extraordinary General Meeting for the incorporation of a limited company in Tunisia.

"ARTICLE 13- TRANSMISSION DES ACTIONS :

Pour l'exercice de ce droit de préemption, l'Assemblée Générale Ordinaire fixe chaque année, le cours de l'action, lequel sera constitué par la valeur nominale augmentée des droits sur les réserves et d'une indemnité équivalente à la quote-part du revenu net social constaté au cours du dernier exercice ou, le cas échéant, diminué de la proportion incombant à l'action, du chef des déficits antérieurs"

The translator has translated as:

"ARTICLE 13- TRANSMISSION OF SHARES

For the exercise of this right of first refusal, the Ordinary General Assembly will set the share price each year, which will be determined by the nominal value plus rights on reserves, and compensation equivalent to the share of the noted net income in the last fiscal year or, where appropriate, decreased in the proportion borne by the action, due to previous losses."

I have kept what I consider to be errors in the original translation I was sent, just in case it affects this.

The part I'm struggling with is "diminué de la proportion incombant à l'action, du chef des déficits antérieurs".
I can't seem to get the version I have been sent out of my head to think clearly..

Thanks in advance for any help.