Straight billiards: what do 47/2 and 71/2 signify?

I have recently stumbled upon an interesting straight billiards page in which the exloits of some recent champions were described.

There seem to be two disciplines called “47/2” and “71/2”. From what I can tell, these aren’t carom games – these disciplines are mentioned alongside One-Cushion and Three-Cushion.

So what are “47/2” and “71/2”?

These are carom (allowed) games to my puny knowledge of billards. the 47 etc refers to the size of the marked square on the table and the n to the number of caroms allowed before having to move to another square. This is to and prevent a boring carom game. try for a better explanation