From what I understand:
If A wants to send to B. he must pay the opening fee of the transaction channel.
After opening the channel and sending the transaction.In the meantime, B is not allowed to send until after the completion of the transaction B can send.
How to calculate the closing fees of the channel "Single and multiple channels"
As far as I understand:
If A wants to send B he needs to "open channel". In order to do so he needs to create Funding on-chain transaction to multisig wallet. This is a standard bitcoin TX that requires both A and B sigs to be further spent.
Closing TX will be spending this funding TX. All transactions in between will not be spent, and any attempts to spend anything but the latest TX will result in punishment for the one who make this attempt.
I.E. Closing channel means posting latest ln tx on blockchain and waiting time-lock to expire.
Cheers!