English to Spanish Law/Patents Insurance

(c) In the event of the amount of the last completed monthly declaration prior to a loss being found to be less than the amount that ought to have been declared, the indemnity by this Policy shall be reduced in the same proportion that the amount of the said declaration bears to the amount that ought to have been declared.

I am lost in the last part of the sentence from "bears to" on.

(e) En caso de que la cantidad de la última declaración mensual realizada antes de una pérdida sea inferior a la cantidad que debería haberse declarado, la indemnización provista por la póliza se reducirá en la misma proporción que la cantidad de dicha declaración...