I can only speculate since I’m an American, but… In the US, sections are like neighborhoods. Oftentimes in the US sections are numerical, but can be letters. I found a map of Freemantle Cemetery in Perth, and it has areas by religion, and lettered sections.
So I bet the Roman Catholic section of your cemetery has a corresponding number.
Nice! Was it buried or just nearby? I bought a trash stabber to help me locate buried stones. Found at least 20+ so far!
Graven Images: New England Stonecarving and its Symbols, 1650–1815 https://www.amazon.com/dp/0819560405/ref=cm_sw_r_apan_glt_fabc_4MZ5GJAQW60HBDK6BJYS?_encoding=UTF8&psc=1
Also be careful with doing rubbings on older stones, photography is a better approach in most cases. A lot of sandstone stones cam shake, and even finger print oils, tape residue, etc can negatively impact older stones.