The seventeen year period to be in profit is near enough.
Say you are entitled to £10,000 a year but defer it for fifty-two weeks.
You would get an additional 5.77% or £577 a year. However, as you didn't get the £10,000 in that first year, it will take (10,000/577) years to make up that £10,000.
That period is seventeen years and four months.