1 FBF is the min amount, take into account that regardless of the amount you are going to lock/deposit there is the transaction fee of 0.001 FBF, so if you deposit 1 FBF you are actually depositing 0.999 FBF or if tou deposit 10 FBF you´ll be depositing 9.999 and so on. the fee is actually the miner´s fee to include and secure the deposit transaction on the blockchain.