I can't see Foc on your clip. Roll numbers normally pertain to Medal Rolls held by the National Archives eg WO 372.
Walter was originally joined Royal Army Service Corps. Service Number DM2/230281. 49th Reserve Battalion. After the time in France, he was Transferred to Class "Z" which is Army Reserve on Demobilization, on 19th Feb 1919 at Woolwich Dockyard.
Home address at this time: Ayton House, Wrekenton, Newcastle.
He received the Victory and British War Campaign Medals (often nicknamed "Mutt and Jeff" when someone only had this pair!). The roll number and page number on the Medal Card for this refers to the actual listing of all members of the RASC who were awarded these medals.