@Marney *******
It is the first 90 day report of every 180 day stamp you get on DTV.
So when you stay the whole 180 days of the stamp and then leave you have to do your first report at day 90 or a few days after, then there will be no second 90 day report because you leave the country at day 180 or before.
When you re-enter it starts all over again wit first 90 day report in person.
Only when you do not leave the country after 180 days and get an in country extension, there will be a second and a third 90 day report, you can do online