IMM 008 is additional dependents, bro, sis etc
Interestingly, if you see the option of dependent type, it say A, B, C - lol but they have remove that option, its only under 18 now so its a mistake by CIC I believe
From the list, select the type of dependant:
Type AThe dependant is under the age of 22 and is single (not married and not in a common-law relationship).Type BThe dependant has been continuously enrolled in and in attendance as a full‑time student at a post-secondary institution accredited by the relevant government authority and has depended substantially on the financial support of a parent either:
since before the age of 22, or
since marrying or entering into a common-law relationship (if it happened before the age of 22).
Type CThe dependant is 22 years of age or older, has depended substantially on the financial support of a parent since before the age of 22, and is unable to provide for himself or herself because of a medical condition