SFR Plus Decoder Remote Control Keyboard

Hello,
The keys on the keyboard have 3 types of inscriptions:
In white ==> direct press to obtain the character inscribed
In green ==> hold down the Alt key (to the left of the space bar) and then press the key with the desired green character
In blue ==> hold down the Fn key (to the right of the space bar) and then press the key with the desired blue character.

The @ is inscribed in green above the down arrow (at the bottom and to the right), so to obtain it press Alt while pressing the key
http://docs.sfr.fr/guide/guide-installation-decodeur-plus.pdf

Note: The remote control of the Décodeur Plus needs to be configured in RF to use the keyboard on the back.
To activate this mode, press the keys 1 + 3 simultaneously until the "Home" key blinks.
See https://assistance.sfr.fr/television/panne-tv-vod/depanner-telecommande-box-tres-haut-debit-thd-4k.html#2

Thank you for your help. I will try tonight and if you don't mind, I will reach out to you again if my problem isn't solved. Thanks again :)