Amqpx.Confirm.next_publish_seqno

You're seeing just the function next_publish_seqno, go back to Amqpx.Confirm module for more information.
Link to this function

next_publish_seqno(channel)

Specs

next_publish_seqno(Amqpx.Channel.t()) :: non_neg_integer()

On channel with confirm activated, return the next message sequence number. To use in combination with register_confirm_handler/2