According to table "BrokerTransportQualityOfService values", there are following values for BrokerTransportQualityOfService:
NotSpecified_0 / BestEffort_1 / AtLeastOnce_2 / AtMostOnce_3 / ExactlyOnce_4 .

The RequestedDeliveryGuarantee in MQTT, however, says:

The BrokerTransportQualityOfService values map to MQTT publish and subscribe QoS settings as follows:
• AtMostOnce_1 is mapped to MQTT QoS 0.
• AtLeastOnce_2 is mapped to MQTT QoS 1.
• ExactlyOnce_3 is mapped to MQTT Qos 2.

Notice that the numbers do not match.

Similarly, in AMQP the RequestedDeliveryGuarantee says:

This matches to the BrokerTransportQualityOfService values as follows:
• AtMostOnce_1 – messages are pre-settled at the sender endpoint and not sent again. Messages may be lost in transit. This is the default setting.
• AtLeastOnce_2 – messages are received and settled at the receiver without waiting for the sender to settle.
• ExactlyOnce_3 – messages are received, the sender settles and then the receiver settles.

The numbers do not match either.

In addition, the spec does not define the behavior when the RequestedDelivery Guarantee is set to a value not specifically listed (e.g. BestEffort_1).