I didn't know how much he paid back in the fourteen years so I checked out the ruling which says "From April 2005 until April 5, 2015, the loan was in deferment

I didn't know how much he paid back in the fourteen years so I checked out the ruling which says "From April 2005 until April 5, 2015, the loan was in deferment or forbearance. " So yes your 5% figure seems about right.