A Solution to the French Taxation Problem with "Livret A"

I’m studying French translation and though I have a grasp of French, I have no understanding at all of economics or tax-rates so any hins here would be much appreciated!

There is a savings account in France known as the Livret A which is popular and tax-free. One of the new government’s latest measures is to increase its ceiling by 25%. In order to combat the potential tax losses this measure might make, the country’s audit board has proposed that the amount of money that surpasses the current ceiling be subjected to tax/social security contributions. I’m afraid I don’t understand how this works – if there is a ceiling, then how can there be an excess amount at all? And doesn’t taxing excess amounts defeat the purpose of the Livret A?

This is what I gather from the French article I found, anyway.

If it’s any help I DID find an article in English explaining it, but I’m still at a bit of a loss as to what it means. Here is what was stated in the English/American article:

“State finance watchdog the Cour des Comptes recently suggested offsetting the loss of tax and charges revenue which will result from the Livret A raise by levying social charges on interest over and above that generated by money invested up to the current ceiling – an idea the government has not ruled out.”

Can anyone here help me out? Thank you !