Hello,
All cryptocurrency amounts on all blockchains are stored as integers to avoid rounding errors associated with floats. They are only converted to floats for displaying to the user. Doing this requires a knowledge of how the currencies are denominated (i.e. how many decimals are used). Bitcoin on layer 1 has 8 decimals, Monero has 12 decimals, Ethereum has 18, every coin can be different.
How are you hooking to the wallets_cryptonote_coins filter? You should change the fields: amount pattern and decimals to reflect the details of your coin.
with regards