Val D'Isere La Daille

Hi all just received a letter from Pierre et Vacance titled "Modification indice loyer"

They want to change the reference terms of the lease back agreement 5 years into the agreement from referencing the increase in the french contruction index to a new index called the "l'indice de reference des loyers" they are saying its a less volatile index than the " l'indice de Cout de la construction"

There is no reference to the the financial implication of signing this document or the implications if I dont sign

Has anyone received this or know what its about .

Thanks

Roy