MySQL Shell dump utility - maximum possible chunk size?
The max value is innodb_buffer_pool_size / innodb_buffer_pool_instances or some integral fraction of that.
But why bother changing the setting?  It should not make much difference.
Reference, and more discussion:  https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_buffer_pool_chunk_size