Modeling Diagram Secret Symbols ?

I am old school MS Access, Oracle, Office VBA. I could not determine what theese symbols mean via online docs or the UI it is not set forth. Does it relate to ordinality? Can someone please provide explanation and decoding? What other synbols are there and their respective meanings? What is different about these 1:M from Dim to Fact table?? (see attached from modeling diagram, the parenthesis like symbol at the ends)