The only way to lose your funds is to reset your wallet during the firmware update, without having any backup. Given that you've got them and assuming you correctly and in the proper arrangement wrote all 24 words there is no reason to worry.

Ledger has an app through which you can check the correctness of your seed which is definitely a recommendation for everyone to be 100% sure they have the correct backup. It is always important to emphasize that the words from the seed are not entered anywhere except in the device itself.

Ledger Recovery Check