Leave that as empty for spouse. If you have any other depends which fall under below categories you have to use that. I think this is question no 12 in dependents section.
From the list, select the type of dependant:
Type A
The dependant is under the age of 22 and is single (not married and not in a common-law relationship).
Type B
The 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 C
The 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.
You can use below link for some more help.
http://www.cic.gc.ca/english/information/applications/guides/5609ETOC.asp#5609E5
