Our wallet that holds crypto coins called "credits." In this wallet, the credits are stored in separate little boxes called UTXOs, or records. To send money to someone, you need to use at least two boxes: one box for the amount you want to send, and another box to pay a small fee.
Right now, there's a problem. If someone gives you 10 credits in just one box, you can't send any money, because you need another box to pay the fee. But if you receive two separate gifts of 5 credits each, in two different boxes, you can send 5 credits and use the other box to pay the fee.
The fee is tiny, only 0.025 credits. When you pay it, you get the leftover fee money back in your wallet.
The Aleo team knows about the problem and is working to make things easier by mid-May.