Which way does an aisle runner typically get unrolled?

I bought a plain white aisle runner from Michael's with the plan of personalizing it myself (which I am looking forward to doing). My issue is that the runner is 75 feet long but the aisle is 60 feet long so I know that 15 feet won't get personalized. I just don't know which 15 feet I should leave plain. Do aisle runners typically start at the alter and go to the back or does the roll start at the back and go to the front? (I am surprised I don't know this but no weddings I have ever been to have had an aisle runner)