After you have sent your Crystals to staking, approximately every 36 hours you will receive technical messages about the crediting of DePool rewards.
Incoming messages look like transactions from the DePool address (read more about DePool) to your wallet address for amounts approximately equal to 0.0001 Crystals, with a minus sign.
By tapping on such a transaction, you can see a message inside about the total amount of funds deposited into the DePool and the current accrued income.
Payment for such messages is from your wallet account because according to the Free TON blockchain mechanism, the transfer fee is charged to both the sender and the recipient. At the same time, the charges are so small that they do not have a significant impact on the wallet balance and are significantly less than the amount of income from staking.