Estimation- Phillips curve forecast

[scboy]

Hi all
I am working on the paper from Stock and Watson 1998, forecasting inflation.
then i follow all the steps and equation( as below regression), it is a forecast of one year horizon using out of sample forecasting method.
I have sample data from 1989 to 2018. But I am wondering at view=> forecast, which period of forecasting sample should I key in according to the paper. is it from 1989 to 2018 or 2017 to 2018??