William Shakespeare

I am so glad you asked! Others might be wondering the same thing. Those numbers indicate where the quote is from within a play. Consider this as an example:

“But soft, what light through yonder window breaks?
It is the east, and Juliet is the sun.”

Romeo

Romeo and Juliet (II,ii,2-3)

The first Roman numeral number in capitals indicates the Act number, in this case Act 2. The lowercase Roman numerals indicate the scene number, here being scene 2. The Arabic numbers - what we’re mostly familiar with - indicates the line number. This is the way I was taught to annotate; I hope it is to everyone’s liking.