QoS Traffic Shaping Explained

Please help me out to implement QoS over ADSL link. I want to prioritize my voice traffic and assign 15% of BW.
Please check the config of my usual WAN link not sure what would be on ADSL.

class-map match-any Client-Signal-Class
 match precedence 3
 match ip dscp af31
 match ip dscp cs3
class-map match-any Client-VOIP-Class
 match precedence 5
 match ip dscp ef
!
policy-map 50Mb-VOIP-PMAP
 class Client-VOIP-Class
  priority percent 10
 class Client-Signal-Class
  bandwidth percent 5
 class class-default
  fair-queue
policy-map 50Mb-VOIP
 class class-default
  shape average 49000000 504000
   service-policy 50Mb-VOIP-PMAP

Not sure what would be the shaping reference BW (Here - 49000000) on ADSL link. Your prompt reply highly appreciated.