The Expected Graduation Date pulls from the student's last Enrollment Row. If a student only has an Enrollment Row (for example) for Grade 11, 2015-2016, but they are not graduating until after Grade 12, 2016-2017, then you must add an enrollment row for Grade 12, 2016-2017, in order for the Expected Graduation Date to pull 2017.
To Add To/Edit a student's enrollment:
1) Navigate to Core > Users > Edit User Profile Data
3) Search/select the student.
4) Scroll down to the lower left under System Information.
5) Select Student Enrollment.
6) Click "Enroll in School" to add an additional School Year/Grade.
The Expected Graduation Date field will then pull from the last enrollment row of the Student Enrollment record.