CC2531EMK: Question regarding Packet Parsing

Hi,

So I sent an AF_DATA_REQUEST to read an attribute ( cluster ID = 0x0001, attributeID = 0x0021 -> getbatteryPercentage)

AF_DATA_REQUEST (0x2401)
    DstAddr: 0x4F16
    DestEndpoint: 0x01
    SrcEndpoint: 0x01
    ClusterID: 0x0001
    TransID: 0x03
    Options: 0x00
    Radius: 0x1E
    Len: 0x05
    Data: ...!. (0x10, 0x03, 0x00, 0x21, 0x00)

And I receive packet right here:

AF_INCOMING_MSG (0x4481)
    GroupID: 0x0000
    ClusterID: 0x0001
    SrcAddr: 0x4F16
    SrcEndpoint: 0x01
    DstEndpoint: 0x01
    WasBroadcast: 0x00
    LinkQuality: 0x3F
    SecurityUse: 0x00
    Timestamp: 0x008CF245
    TransSeqNumber: 0x00
    Len: 0x08
    Data: ...!.. . (0x08, // START OF ZCL HEADER
                    0x03, 
                    0x01, // END OF ZCL HEADER
                    0x21, // 0x0021 ATTRIBUTE ID
                    0x00, 
                    0x00, // Status?
                    0x20, // 0x8820 is the value? is out of range
                    0x88)

Don't really know how to read it.