Vest

Have a pattern for knitted vest size 40 would like too make this for a size 35 bust insteadthey are using size6&7 needles and casting on 207 sts.can anyone help me change this, would appreciate any help. thanks Nanaerma

It would help us a little more if you linked to the pattern, or a little more information about it. Like what gauge, what yarn and needle size in the pattern and so on…