Nominal Interval is what we find in card info.
Real Interval is
Today - Latest Review Date
e.g. this card is suspended in 2018 and I unsuspend it after more than 2 years. The Nominal Interval is 1 day. But Real Interval is more than 2 years.
When Real Interval is much longer than Nominal Interval, we should take Real Interval as Interval, but not Nominal Interval.
(Or we can calculate the average, Interval = (Real Interval + Nominal Interval)/2 )
And hard interval should be
Real Interval * 120%(hard interval ratio)