Now that the multisig is created and funded, Alice, Bob, and Charlie want to make a transaction.

Whenever a multisig transaction (call) is initiated, whoever initiated it must reserve a deposit of a little more than 20 CERE. The exact amount depends on how large is the threshold of the multisig. This reserve is released when the transaction is approved or canceled. The rest of the signatories don't need to reserve a deposit.

This is done to prevent bloating of the chain state from multisig calls that are initiated but never completed. So, whoever plans to initiate calls needs to have at least 20.5 CERE transferable balance in their account to be able to pay for the deposit.