When running the message scanner, it reports maximumMessageLength as 4194304, but the queue manager and/or queue value are larger than that.
The value shown is the limit as observed by the message scanner, which is a client application. This size is determined by the minimum of three attributes: the queue manager maximum, the queue maximum and the channel maximum. Thus, if you set the queue manager and queue maximum larger than the default value, but the channel is set to a lower size, this is the reported value.