A lot of regulations depend on your status in the PhD program, such as G3, G4, or G5. You are:

• G3 if you are currently in year 1 of the PhD and have completed less than 24 credits of graduate-level course work, including courses taken prior to joining the PhD program.
• G5 once you have been advanced to candidacy (this usually happens in the summer between year 3 and year 4).
• G4 if you are neither G3 nor G5. If you entered the PhD program with a completed master’s degree, you are usually classified as G4 from the start.

+) Now you must be wondering what G1 and G2 mean:

https://www.stonybrook.edu/sb/graduatebulletin/current/admissions/academic-level/index.php