The symbols are Battallion Numbers
"Sarcee Training Camp, set up to train soldiers to prepare for WW1 was located near the base of Signal Hill (then called Cairn Hill) (actual location just south of Glenmore Trail)
Because many of the trainers were from the United Kingdom, they saw an opportunity to utilize the abundance of field stones as a training exercise, to display the soldiers battalion numbers, as so often was done in the UK. So in 1915-16 field stones, were carried up the hill and arranged by the soldiers in their Battalion numbers
Calgary: 137, Lethbridge; 113, Red Deer: 151 and Edmonton 51.
Those soldiers from the 137 Battalion, who survived the war, came home with a mission to save the Stones of Signal Hill, which had become a symbol of their lost comrades. During their struggle to preserve this site they were told by the provincial government at the time,"
[ From an article on phylliswheaton.com that no longer exists ]
The hill features 16,000 stones hauled by soldiers and arranged to form four numbers (137, 113, 151 and 51). The numbers correspond to the four battalions of the Canadian Expeditionary Force who trained in that area before leaving to fight in World War 1. Battalion Park officially opened on November 3, 1991.