the mystery of numbered grass

In order to prevent a rant at a: Fuji's delay in fixing and returning my proper camera, b: the bike shop not yet restocking on my preferred tyre which has led to c: my fourth puncture in seven days from broken ned-glass on the bike path between Trinity and Craigleith I shall post this.

Why are there little posts with numbers on all round St. Andrew's Square? There are no similar posts around Charlotte Square. Are they the part of the garden allotted to the inhabitants of the building of that number? Do they refer to a particular tree? Is it a learning-aid for the childs of the posh-ass folk living in the vicinity who would order their nannies to circumtrundle the park? Mayhap it is an art installation.