French to English Other Human Resources Working rights

As a matter of fact I am not asking for a translation of this term ("avancer son salaire" )as such. I presume it means continuing to pay her salary. However, I have a problem with the text (see below) in which it ocurs, which I thought I understand perfectly-the French seems to be pretty easy- but which seems to be contradictory and so I am worried I may have missed the point. The text is about regulations in force concerning health and safety at work, specifically here the employers' obligation to pregnant employees. As I understand it, the first sentence is saying that the employer is under an obligation to reallocate the employee to day work while paying the same salary as before. In the second sentence I read that the
difference in revenue resulting from the change of post will be reimbursed to the employee by the health insurance.
My question is how can the employee be reiumbursed for a difference in revenue when the previous sentence clearly states that the employee will be paid her previous salary? I don't get it.
I have read this five or six times and it still looks like a complete contradicition to me. Have I misunderstood something? Help will be very much appreciated!!

Yorick Jenkins

Here is the text:

L'employeur est tenu de l'affecter à un poste de travail de jour avec obligation pour lui d'avancer son salaire antérieur.
La différence de revenu résultant du transfert de poste est à charge de la caisse de maladie et sera remboursée.