What does “enrolled in 6 or more units?” mean?

I’m filing a mother family size certification to my college and in one of the sections it questions if anyone in the family is “enrolled in 6 or more units?”. I have to choose either Yes or No. So what does it mean?
Brother attends a art institute so not sure if that will affect this form.

Read the full article here:

What does “enrolled in 6 or more units?” mean?