Thank you for asking this question in the Support Community. You cannot set AF3. According to RFC 2597 the AF codepoints are as follows:
AF11 = ' 001010'
AF12 = '001100'
AF13 = '001110'
AF21 = '010010'
AF22 = ' 010100'
AF23 = '010110'
AF31 = '011010'
AF32 = '011100'
AF33 = ' 011110'
AF41 = '100010'
AF42 = '100100'
AF43 = '100110'
Typically, AF3 refers to AF41, AF42, and AF43, which you can set with the set dscp af<xx>, where "<xx>" represents the AF value. For example,
ROUTER-NAME(config-qos-map)# set dscp af41
I hope this answers your question, but do not hesitate to reply with additional questions. Also, for further reference, please review Configuring QoS in AOS.
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