for issb candidate.

in issb ,they check these topic in your
selves ,so please prepared before you going to issb

*about your intro(your,ur family,education,etc)
*you education (about some question everyday science, physics etc)

they assumed u are graduate so they check you mental math which should be better than long course candidate.

*you are pakistani ,so should know about pakistan,army , government,surrounding,laws etc

*you are Muslim ,so should know about basic knowledge about islam.

regards