Yep, it’s explained in the coin adapter settings.

For reference, fixed fees are an amount that is charged on each transaction. Proportional means that the transacted amount is multiplied by the fee “proportion” and therefore the fee paid for the transaction is a fraction of the total transacted amount.

From the documentation’s glossary section:

Fees are subtracted from user accounts and remain with the wallet. For every coin, there is one wallet that is split between all users with the has_wallets capability. In the case of withdrawals, the fees are first used to pay for the blockchain’s network fees, and any remaining fees stay with your site’s wallet. In the case of internal transfers between users, the entirety of the paid fees is subtracted from the sender’s balance and remains with your wallet, since there is no blockchain transaction. When you visit the *coin adapters* screen in your admin area, you can see the total of user balances for each coin, and the balance of the wallet. These amounts do not have to be the same. As users perform transactions and pay fees, these fees will be subtracted from the user balances, but not from the wallet balance.